My immediate thought as well, always best to test materials. Put some in an old sauce pan, add engine oil and stick on a camping gas stove, well away from the house, and cycle a few times and see what happens to it.........
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PollyMobiles Rebuild
- Thread starter pollyp
- Start date
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pollyp
Club Member
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pollyp
Club Member
parents pug 307 has been blowing badly and I thought the downpipe I welded had cracked again.
so I removed the downpipe and it turns out my welded bracket was all fine and it's actually the welded flange which has rusted away
wirebrushed it clean
after welding together, it's now all quiet
so I removed the downpipe and it turns out my welded bracket was all fine and it's actually the welded flange which has rusted away
wirebrushed it clean
after welding together, it's now all quiet
OP
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pollyp
Club Member
nice as usual ! that peugeot thing can't you just throw it all in the bin ?
the whole car or the downpipe
it ain't my car and rather not spend much on it myself.
it's my only commute whilst fixing kasandra so I just needed to fix these minor issues quickly & cheaply
OP
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pollyp
Club Member
brass disc arrived. machined it down but accidentally went too far at 48.5mm rather than 49.5mm diameter ordered another one
drilled the screw holes
old 45mm plate vs new 49mm
this'll make breathing abit different eh
all assembled clean & shiny & simpler
just need to remake the butterfly disc & seal up those holes
ordered another one
drilled the screw holes
old 45mm plate vs new 49mm
this'll make breathing abit different eh
all assembled clean & shiny & simpler
just need to remake the butterfly disc & seal up those holes
OP
OP
pollyp
Club Member
yup original. I'll just nip em up real tight with a dab of threadlock.
Ok Paul, not being critical, just conditioned to mentally running an FMEA on anything that changes/gets redesigned........i.e. 'what can go wrong?' 'what are the consequences of it going wrong?' 'what can be done to stop the original possible failure' and then start the loop again 'what can go wrong with the change that prevents the initial failure possibility?' etc etc......
I originally designed high speed production line machinery and to go through this procedure (on major projects, formally, with an FMEA committee,) could save lots of problems in the future.
There's no strain on a spindle so FEA would be off little help?
We just loctite the screws from factory and have never had one come loose.... Would be catastrophic if it did happen though!
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We just loctite the screws from factory and have never had one come loose.... Would be catastrophic if it did happen though!
Sent from my CLT-L09 using Micra Sports Club mobile app
No strain, but potentially lots of vibration and fuel to attack any chemical fixing
Any fuel resistant locking agent would OKLocktite 243 here
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pollyp
Club Member
Fitting Dual Exhaust Pipe For Neilio's Ford Focus
A m8 I see at the regular car meets needed help with installing a 2nd-hand Dual tail pipe exhaust onto his diesel Focus to replace the boring hidden single pipe
he also wanted to remove the backbox to try get more noise from the muffled TDI
chopped & bypassed the silencer
so here's the new exhaust he brought online and after close inspection, holy mother jeesus christ this is by far the WORST exhaust I've ever seen with stevie wonder pigeon poo welding
just LOOK AT IT!
looking inside was shocking
absolutely no way I'm fitting this shyte work, so decided I'll have to salvage the good bits and reconstruct the whole thing from scratch
turning from a simple hour job into a weekend mission
A m8 I see at the regular car meets needed help with installing a 2nd-hand Dual tail pipe exhaust onto his diesel Focus to replace the boring hidden single pipe
he also wanted to remove the backbox to try get more noise from the muffled TDI
chopped & bypassed the silencer
so here's the new exhaust he brought online and after close inspection, holy mother jeesus christ this is by far the WORST exhaust I've ever seen with stevie wonder pigeon poo welding
just LOOK AT IT!
looking inside was shocking
absolutely no way I'm fitting this shyte work, so decided I'll have to salvage the good bits and reconstruct the whole thing from scratch
turning from a simple hour job into a weekend mission
OP
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pollyp
Club Member
constructed the tail pipe to the correct distance
bypassed the backbox with a straight pipe. went for a quick drive without any backbox or tail pipe and for a TDI it's surprisingly quieter than mine, sounds normal. wtf was the point of that huge silencer then?
initially the pipes were gonna sit under the bumper but Neilio says it might be too low for bumps and doesn't mind having to cut holes
next day I marked & dremelled some holes in the rear bumper to raise the pipes further up to sit much better like this
but disaster, whilst chopping it at an awquid angle I nudged the serrated dremel blade for a millisec and OUCH
went to the sink to see how bad it was and OMG blood's flowing at quite a rate
tried a plaster over it but it seeps out! crap what do I do? fear I hit an artery/vein
managed to bandage it up from my car's little emergency 1st aid bag, sister rushed over to help.
worrying I might need stitches in hospital if it didn't stop bleeding and gotta finish this exhaust on a sunday for the guy.
thankfully the bandage & gloves held up and it stopped later on
tacked & welded all the pipes & hangers on
much better
fits like a glove
now that looks the business
bypassed the backbox with a straight pipe. went for a quick drive without any backbox or tail pipe and for a TDI it's surprisingly quieter than mine, sounds normal. wtf was the point of that huge silencer then?
initially the pipes were gonna sit under the bumper but Neilio says it might be too low for bumps and doesn't mind having to cut holes
next day I marked & dremelled some holes in the rear bumper to raise the pipes further up to sit much better like this
but disaster, whilst chopping it at an awquid angle I nudged the serrated dremel blade for a millisec and OUCH
went to the sink to see how bad it was and OMG blood's flowing at quite a rate
tried a plaster over it but it seeps out! crap what do I do? fear I hit an artery/vein
managed to bandage it up from my car's little emergency 1st aid bag, sister rushed over to help.
worrying I might need stitches in hospital if it didn't stop bleeding and gotta finish this exhaust on a sunday for the guy.
thankfully the bandage & gloves held up and it stopped later on
tacked & welded all the pipes & hangers on
much better
fits like a glove
now that looks the business
OP
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pollyp
Club Member
inside the standard inlet manifold are these roughly cut edges, not good for airflow
so after a lot of dremel grinding, it's much smoother inside and trimmed a bit of the lip to clear the larger 50mm TB
give it a good thorough wash in detergent to clear out all the mess
the 1st butterfly plate was machined too small accidentally, so ordered another brass disc
machined down to precisely match the 49.57mm bore and now it fits extremely snug with no light peeking through the closed valve like the original
machined this plug to seal off the hole where the MAF was
so after a lot of dremel grinding, it's much smoother inside and trimmed a bit of the lip to clear the larger 50mm TB
give it a good thorough wash in detergent to clear out all the mess
the 1st butterfly plate was machined too small accidentally, so ordered another brass disc
machined down to precisely match the 49.57mm bore and now it fits extremely snug with no light peeking through the closed valve like the original
machined this plug to seal off the hole where the MAF was
OP
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pollyp
Club Member
I was swearing soo much at how bad this was botched together, a double face-palm wouldn't be enough for this embarrasement
Just checking you've left a little clearance for the butterfly?
Obviously when it gets warm it'll expand a little and you don't want it sticking open haha!
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Obviously when it gets warm it'll expand a little and you don't want it sticking open haha!
Sent from my CLT-L09 using Micra Sports Club mobile app
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pollyp
Club Member
yup I've filed the sides near the pivot abit narrower to allow the butterfly to rotate
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pollyp
Club Member
lockwired the screws on the belt tensioner so it'll never vibrate loose again
now with the engine side done, time to prep the engine bay.
removed the master cylinder for access to a rusty corner in the bulkhead
looks like water had seeped past the old sealant and rusted that panel join but thankfully the thicker strut top is still solid and I just need to repair the tin foil inner section
now with the engine side done, time to prep the engine bay.
removed the master cylinder for access to a rusty corner in the bulkhead
looks like water had seeped past the old sealant and rusted that panel join but thankfully the thicker strut top is still solid and I just need to repair the tin foil inner section
OP
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pollyp
Club Member
chopped out the rot
found yet more holes on the scuttle panel, all these plastic clips simply trapped moisture
getting abit carried away with cutting tools
had to stop myself at some point like..
more trapped rust
gave it a lick of red oxide paint that a m8 suggested
welded up the panels
sealed all the gaps with Tigerseal (grinded all the welds smooth next day btw)
undersealed the whole bulkhead
part of the engine loom near the gromet was left exposed for years, so while unravelling the old hardened oily tape to clean the wires, I ended up opening the whole thing apart to re-do neater
thing's never simple.
1 curious fix always leads to another several more fixes
found yet more holes on the scuttle panel, all these plastic clips simply trapped moisture
getting abit carried away with cutting tools
had to stop myself at some point like..
more trapped rust
gave it a lick of red oxide paint that a m8 suggested
welded up the panels
sealed all the gaps with Tigerseal (grinded all the welds smooth next day btw)
undersealed the whole bulkhead
part of the engine loom near the gromet was left exposed for years, so while unravelling the old hardened oily tape to clean the wires, I ended up opening the whole thing apart to re-do neater
thing's never simple.
1 curious fix always leads to another several more fixes
OP
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pollyp
Club Member
wrapped up each circuit and then bunched them into the final loom
reinstalled the PAS system so I can replumb the low pressure return side over to the un-used automatic gearbox cooler in the radiator and get rid of that old PAS cooler
the automatic cooler is too small @ 8mm
so I threaded an adapter to bring it up to 10mm for the PAS system
begin planning the route
reinstalled the PAS system so I can replumb the low pressure return side over to the un-used automatic gearbox cooler in the radiator and get rid of that old PAS cooler
the automatic cooler is too small @ 8mm
so I threaded an adapter to bring it up to 10mm for the PAS system
begin planning the route
LiamC
I've ruined my car ?
I have always wondered if any people would take advantage of that secondary part of the radiator for those who use the thick auto rads for oil cooling etc but never seen it done
OP
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pollyp
Club Member
indeed I once thought about using it as oil cooler but seemed abit risky if it went wrong
OP
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pollyp
Club Member
had to go through a few iterrations of routes to keep the bends few & simple and out the way
the final simple layout was to just plumb the return line through the empty chassis rail (which would also be great for hiding the engine loom)
it goes straight across to the other side of the radiator avoiding the red hot exhaust
and down to the little cooler (and if the radiator exchanger wasn't helping, I could just join the two pipes up to form the same original PAS cooler)
the final simple layout was to just plumb the return line through the empty chassis rail (which would also be great for hiding the engine loom)
it goes straight across to the other side of the radiator avoiding the red hot exhaust
and down to the little cooler (and if the radiator exchanger wasn't helping, I could just join the two pipes up to form the same original PAS cooler)
Mine does that It's weird as
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pollyp
Club Member
indeed it was a really annoying detail, so with the engine sloping at 1deg
I removed the RH mount, dropped the engine down till it sat level and the front mount holes sit where it should, and redrilled this hole 25mm further down
later figured I could just fit some 7mm spacers so the hole didn't have to be soo low and stop the mount getting too close to the chassis
now it sits nicely level
continue quickly fitting everything in
checking the turbo. considering it's been running at full boost with zero oil pressure for a few seconds while going uphill when the forged engine blew up, I'm so lucky the bearings are still snug and nothing's damaged
almost there
I removed the RH mount, dropped the engine down till it sat level and the front mount holes sit where it should, and redrilled this hole 25mm further down
later figured I could just fit some 7mm spacers so the hole didn't have to be soo low and stop the mount getting too close to the chassis
now it sits nicely level
continue quickly fitting everything in
checking the turbo. considering it's been running at full boost with zero oil pressure for a few seconds while going uphill when the forged engine blew up, I'm so lucky the bearings are still snug and nothing's damaged
almost there
OP
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pollyp
Club Member
It's been an interesting and very exhausting week resolving all her little issues so here's what happened:
Everything assembled.
Figured this old bottle of octane booster had the right size neck to use as a coolant filler funnel, it makes filling & bleeding soooo much easier & cleaner.
Battery has been flat at 11v for the past 3 months so I trickle charged it back to 12.6v
primed the oil, took a few dozen slow turns for the dry engine to build enough oil pressure before it cranked more freely which was a relief.
just realised in time that I forgot to tighten the fuel rail hose before I primed it that could've been bad with fuel spraying everywhere
video of the 1st fire ups
after all that priming, the battery & jump starter was totally flat
so I hooked up a battery from the Peugeot to boost it
engine immediately fired up on the 1st crank! she friggin works
PAS tank quickly runs empty & whines and the old belt was slipping, so I added more fluid till it builds pressure and the cooler hose POPs off! spewing red oil across the floor
tried a tighter clamp but still leaked so I just bypassed the cooler for now.
the PAS kept churning the oil into foam and whenever I add fluid, turn steering or turn it off, the compressed foam gushes back out the tank into a mess, as if there's a blockage or the hoses are stretching
syphoned & replaced the PAS oil and managed to bleed it.
with all fluids bled & warm, time for her first drive
trying to steer out the garage and bloody hell** the rebuilt LSD is soo stiff, steering is soo stiff when the diff locks, the brakes are probably binding slightly and the machined throttle plate sometimes doesn't fully shut & will need more smoothing, but damn I forgot how hardcore she is to drive and missed her choochoo noises
next day I replaced the belt, loosened the sticky brakes, straighten the alignment and measured the LSD preload was off the chart
woops built the LSD with too many plates & not enough preload so it becomes insanely biased. loose on left turns but locks totally aggressive & understeery on tight slow right turns (great for launching although tyres are now old & hard, bad for u-turns)
replaced all the stratchy silicone hoses in the PAS lines with stiffer rubber.
the PAS had tons of trapped air and I figured how to bleed it by:
- turning full lock, start engine briefly, it sucks in fresh clean oil till the tank ran low, stop engine before it churns.
- turn other way, syphon out any foamy oil, refill tank, restart engine, sucks yet more fresh oil till a big pocket of air escapes from the return pipe, stop engine.
- rinse/repeat till there's no more foaming.
so I went for a proper test drive at night and it's soo nice to have her back, she feels quite different after spending 3 months in a peugeot
the only major issue was a serious leaning-out & knocking at specific rpm in 1st/2nd gear at WOT full boost
I swapped back to the standard TB and the AFR was back to normal
checking the mapping readout, it seems the enlarged TB was flowing a lot more air than the map expected throwing the mixture wayy off at high load
I also discovered this map I last ran on the standard block with the cracked ringlands had this worrying closed-loop section as the boost begins to build wtf was I thinking? maybe that error could've caused the detonation all along?
reloaded the original mapping for the turbo'd standard block & hope she behaves now
after discovering the bigger shiny TB flows too much and would require remapping to properly use it,
rather than simply slap the old ugly dirty standard TB on, I prefered the smooth flow of the new one so I decided to machine this simple removable restriction tube which slides into the new TB to reduce it back from 50mm to normal 45mm
and IT WORKED wow the AFR are sooo perfect and damn she pulls hard like a train
the important thing to note with this fresh standard engine is she no longer drinks or burn/smokes oil, all cylinders are an equal 11.1bars and the crank spins sooo smooth (the old forged engine shaked a lot)
this is probably the best engine I've ever built.
replaced her front grill cos I snapped the old grill mounts & don't need the cooling gaps anymore. the odd green gives her a superhero mask
there's been an odd oil staining in the engine bay and traced it down to simply forgetting to fit the big washer on the crank pulley doh!
filmed a cheeky rev too, behold at how she has quit smoking & turned into a good girl
Everything assembled.
Figured this old bottle of octane booster had the right size neck to use as a coolant filler funnel, it makes filling & bleeding soooo much easier & cleaner.
Battery has been flat at 11v for the past 3 months so I trickle charged it back to 12.6v
primed the oil, took a few dozen slow turns for the dry engine to build enough oil pressure before it cranked more freely which was a relief.
just realised in time that I forgot to tighten the fuel rail hose before I primed it
that could've been bad with fuel spraying everywhere
video of the 1st fire ups
after all that priming, the battery & jump starter was totally flat
so I hooked up a battery from the Peugeot to boost it
engine immediately fired up on the 1st crank!
she friggin worksPAS tank quickly runs empty & whines and the old belt was slipping, so I added more fluid till it builds pressure and the cooler hose POPs off! spewing red oil across the floor
tried a tighter clamp but still leaked so I just bypassed the cooler for now.
the PAS kept churning the oil into foam and whenever I add fluid, turn steering or turn it off, the compressed foam gushes back out the tank into a mess, as if there's a blockage or the hoses are stretching
syphoned & replaced the PAS oil and managed to bleed it.
with all fluids bled & warm, time for her first drive
trying to steer out the garage and bloody hell** the rebuilt LSD is soo stiff, steering is soo stiff when the diff locks, the brakes are probably binding slightly and the machined throttle plate sometimes doesn't fully shut & will need more smoothing, but damn I forgot how hardcore she is to drive and missed her choochoo noises
next day I replaced the belt, loosened the sticky brakes, straighten the alignment and measured the LSD preload was off the chart
woops built the LSD with too many plates & not enough preload so it becomes insanely biased. loose on left turns but locks totally aggressive & understeery on tight slow right turns
(great for launching although tyres are now old & hard, bad for u-turns)
replaced all the stratchy silicone hoses in the PAS lines with stiffer rubber.
the PAS had tons of trapped air and I figured how to bleed it by:
- turning full lock, start engine briefly, it sucks in fresh clean oil till the tank ran low, stop engine before it churns.
- turn other way, syphon out any foamy oil, refill tank, restart engine, sucks yet more fresh oil till a big pocket of air escapes from the return pipe, stop engine.
- rinse/repeat till there's no more foaming.
so I went for a proper test drive at night and it's soo nice to have her back, she feels quite different after spending 3 months in a peugeot
the only major issue was a serious leaning-out & knocking at specific rpm in 1st/2nd gear at WOT full boost
I swapped back to the standard TB and the AFR was back to normal
checking the mapping readout, it seems the enlarged TB was flowing a lot more air than the map expected throwing the mixture wayy off at high load
I also discovered this map I last ran on the standard block with the cracked ringlands had this worrying closed-loop section as the boost begins to build
wtf was I thinking? maybe that error could've caused the detonation all along?
reloaded the original mapping for the turbo'd standard block & hope she behaves now
after discovering the bigger shiny TB flows too much and would require remapping to properly use it,
rather than simply slap the old ugly dirty standard TB on, I prefered the smooth flow of the new one so I decided to machine this simple removable restriction tube which slides into the new TB to reduce it back from 50mm to normal 45mm
and IT WORKED
wow the AFR are sooo perfect and damn she pulls hard like a train the important thing to note with this fresh standard engine is she no longer drinks or burn/smokes oil, all cylinders are an equal 11.1bars and the crank spins sooo smooth (the old forged engine shaked a lot)
this is probably the best engine I've ever built.
replaced her front grill cos I snapped the old grill mounts & don't need the cooling gaps anymore. the odd green gives her a superhero mask
there's been an odd oil staining in the engine bay and traced it down to simply forgetting to fit the big washer on the crank pulley
doh!
filmed a cheeky rev too, behold at how she has quit smoking & turned into a good girl
I've had no problems with my GA15 TB it was tuned with it though...
That would tie in, mine is running a fabricated (not by me) inlet manifold, I don't have an idea about how much power it gained but it's behaving itself, the MAF sensor we determined before tuning was the same item in the GA15 as the CG13 so if you were able to compare raw signal outputs from the MAF in both cases it might give an idea of whether it's able to use that extra flow capability.
I wonder if much of the benefit of ITBs (not the better throttle response I know about that) is just getting rid of a restrictive inlet manifold?
The predominant advantage of most aftermarket inlet setups is removing the restrictive standard manifolds, however ITB's or twin bodies do flow more air than the standard body and have better response too
Sent from my CLT-L09 using Micra Sports Club mobile app
Sent from my CLT-L09 using Micra Sports Club mobile app
https://www.fusionfabs.co.uk/nissan-micra-plenum-chamber one of these would flow better
Sent from my SM-G901F using Tapatalk
Sent from my SM-G901F using Tapatalk
OP
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pollyp
Club Member
it seems enlarging the tight throttle body neck by just a few mm makes a big difference in peak airflow till it maxes out the next restriction in the system, such as the tiny exhaust manifold and the rough/poor flowing inlet manifold, and even more with boost.
this will obviously throw the MAF values wayy off spec so the ECU would need recalibrating/remapped back to safe levels.
hmm looks easy enough to make 1 day
this will obviously throw the MAF values wayy off spec so the ECU would need recalibrating/remapped back to safe levels.
https://www.fusionfabs.co.uk/nissan-micra-plenum-chamber one of these would flow better
hmm looks easy enough to make 1 day
OP
OP
pollyp
Club Member
so after driving her for the past week with the poor cold weather getting her all filthy, here are a few findings:
- the Odyssey gel battery seems to be struggling more to hold enough charge nowadays. leaving it at 11v for the past 3 months since blowing up the engine certainly didn't help it. just powering up the LED lights or headlights or ignition for over 10mins quickly drains all the juice till it struggles to crank.
- the gearbox input shaft end roller bearing sounds like it's worn. it rattles badly when idling with stone cold gear oil and slightly better once warmed up but doesn't whine under load in-gear so the deep-groove ball bearing clutch end is probably ok.
- LSD preload values are now at both extreme ends of the scale. the deceleration ramp shows 0Nm while the acceration ramp is still over +200Nm (turning into a 1-way diff) so it's definately setup wrong now with too many plates and no enough preload.
due to the biased diff layout, LH turns are normal but whenever I turn right it locks up tight and either chatters loudly with the clutch depressed or skips the inside tyre. 3 point turns are a nightmare. so I definately need to reconfigure the LSD next time I remove the gearbox.
- there's no longer any major oil leak other than a slightly staining turbo drain fitting, and she doesn't burn or smoke any oil at all nowadays
- catch cans are working really well with this new engine, capturing a massive 400ml per 1000miles compared to the previous 150-200ml, and it's mainly water & fuel vapour.
- AFR mixtures are running perfect and even when coasting in high-gear, where she used to richen 9-11afr once under 1700rpm, it stays above 14afr
- old wiper motor connectors were recently getting rusty & faulty so I dismantled, wirebrushed & greased all the terminals and working nicely again.
- the Odyssey gel battery seems to be struggling more to hold enough charge nowadays. leaving it at 11v for the past 3 months since blowing up the engine certainly didn't help it. just powering up the LED lights or headlights or ignition for over 10mins quickly drains all the juice till it struggles to crank.
- the gearbox input shaft end roller bearing sounds like it's worn. it rattles badly when idling with stone cold gear oil and slightly better once warmed up but doesn't whine under load in-gear so the deep-groove ball bearing clutch end is probably ok.
- LSD preload values are now at both extreme ends of the scale. the deceleration ramp shows 0Nm while the acceration ramp is still over +200Nm (turning into a 1-way diff) so it's definately setup wrong now with too many plates and no enough preload.
due to the biased diff layout, LH turns are normal but whenever I turn right it locks up tight and either chatters loudly with the clutch depressed or skips the inside tyre. 3 point turns are a nightmare. so I definately need to reconfigure the LSD next time I remove the gearbox.
- there's no longer any major oil leak other than a slightly staining turbo drain fitting, and she doesn't burn or smoke any oil at all nowadays
- catch cans are working really well with this new engine, capturing a massive 400ml per 1000miles compared to the previous 150-200ml, and it's mainly water & fuel vapour.
- AFR mixtures are running perfect and even when coasting in high-gear, where she used to richen 9-11afr once under 1700rpm, it stays above 14afr
- old wiper motor connectors were recently getting rusty & faulty so I dismantled, wirebrushed & greased all the terminals and working nicely again.
SuperUno
Buy & Sell Member
Not my work but makes sense... relating to our TB discussions:-
Bigger Throttle body nonsense…
I love my dyno, it’s great.
It doesn’t suffer from any placebo effects, it doesn’t read biased rubbish on the internet, it doesn’t try to sell you anything or try to convince itself that its most recent purchase was not a total waste of money and it doesn’t flatter with “suits you, Sir” lies; it just measures what is being produced and shows it, warts an’ all.
So, now that’s out of the way, let’s look a little bit at HOW engines breathe, since that’s what induction changes seemingly set out set out to improve…..
Suck, squeeze, bang, blow right? Yes of course, mostly.
However, imagine that a given engine has a cylinder capacity of say, 3000cc, so each revolution it would DISPLACE 1500cc (1.5 litres), and that it’s running at 6000 rpm; that’s 100 revs per second so 50 CYCLES per second and thus, 150 litres per second @ 100% Volumetric Efficiency (VE). Think about that, a hundred and fifty litres per SECOND.
Well, given how fast that is all happening the VE isn’t going to be anything like 100%, is it, because there’s so little time to fill and empty the cylinders, right?
All the little restrictions along the way; air filter, trunking, intake silencer, throttle body, plenum chamber, intake runners, ports in the cylinder head, past the valves (which are closed for more than half of the time) and that’s just to get TO the cylinder, after all that it’s still got to get out….
SO…. what would you realistically expect the VE to be in such circumstances? Well, if you were to put a huge vacuum cleaner sucking at an unrestricted rate of 150 l/s (saving the piston’s uppy-downy motions from doing the job) pulling air through to the cylinders you’d get, perhaps 75% of the potential unrestricted flow. In that case there’s 25% of the potential flow lost to the restrictions.
You’re never going to get ZERO restriction because there’s far too much other necessary stuff in the engine and engine bay to fit filter, trunking, manifold and ports of sufficient proportions to have zero restriction.
A modern engine is pretty good out of the box and you wouldn’t ever expect as much as a 5% improvement in flow without drastic changes, and those very same drastic changes would likely make things worse in other ways. So, best ways up you might see 78 or 79% of the potential flow.
How come then, a typical modern high-performance road car engine has a VE of as much as 120%? Yes, a 3 litre engine would breathe as much as 3600cc in two revolutions!
With its silly uppy-downy pistons, pulling air past valves that are only open for typically 36% of the time, through ports that often have rough surfaces and uneven profiles, through often convoluted trunking and in from the outside world through a filter that only has open areas of a few microns. It cannot possibly be, surely? That’s over 50% more than the possible flow when the valves are only open for 36% of the time and the piston is only on the induction stroke for half of a revolution. “Get the ducking stool ready people, something isn’t right…..”
Well it can and it does, using PRESSURE WAVES. Tuning pressure waves is what it’s all about. Camshafts, exhausts, intake systems SHOULD all work absolutely together to harness the highs and lows of the pressure waves to best effect; so effective in fact that it amounts to a very significant supercharging effect.
Flow plays a very low second fiddle to pressure waves when it comes to tuning, because the difference that a loss of wave amplitude makes is far greater than the potential flow ‘increase’ from having a larger diameter and guess what? When the diameter of a pipe increases, the amplitude of the waves within it reduce because the molecule compression occurs over a greater area (the surface area, if you will, of the pipe section), so while the static flow may be imagined to be greater, the dynamic flow is actually considerably less.
For example, just look at a GT or F3 airbox - the airbox is huge to harness the pressure waves but the inlet FLOW is through a tiny little inlet restrictor, and despite this the engines still make PLENTY of power.
A flat six engine (all sixes actually for a specific reason that we don’t need to entertain here) is particularly well suited to harnessing the pressure waves that travel back and forth into, as well as across, the manifold if allowed to. They can make a huge difference to the VE at some engine speeds. This is why the (not stupid) design engineers at Porsche have gone to such great lengths to make best use of the pressure waves by employing various flaps in the system to either block or allow passage of pressure waves within the system.
When developing their engines manufacturers will do many, many hours of simulation work. After that they will make many test pieces, probably at least twenty different head casting designs, fifty camshaft profiles, piston crown designs, valve head shapes, compression ratios, manifold designs, you name it. At each engine test, a zillion sensors and probes are mounted all over the engine measuring everything that can be measured.
DO YOU NOT THINK THAT AT SOME POINT IN ALL THAT IT WOULD HAVE BECOME APPARENT TO THEM THAT IT NEEDED A BIGGER THROTTLE BODY?
No, of course not, they’re all stupid those Germans, right?
It takes Fred in his shed with probably zero engine design expertise, to think “Gad Daim, I can fit me a bigger throddle on there an’ life will be reeeeeal gewd….”
If only things were that simple…..
In the vast majority of cases BIGGER THROTTLE INTAKES DON’T WORK so save your money.
In every single Porsche case that I have EVER had on the dyno, NO bigger intake has made an improvement, and almost ALL has made less area under the curve than stock.
When a vendor selling parts says “There’s a 25 bhp difference with this Big-Boy Carlos Fandango intake Sonny Jim” just consider whether he means UP or DOWN!!!!!!
Bigger Throttle body nonsense…
I love my dyno, it’s great.
It doesn’t suffer from any placebo effects, it doesn’t read biased rubbish on the internet, it doesn’t try to sell you anything or try to convince itself that its most recent purchase was not a total waste of money and it doesn’t flatter with “suits you, Sir” lies; it just measures what is being produced and shows it, warts an’ all.
So, now that’s out of the way, let’s look a little bit at HOW engines breathe, since that’s what induction changes seemingly set out set out to improve…..
Suck, squeeze, bang, blow right? Yes of course, mostly.
However, imagine that a given engine has a cylinder capacity of say, 3000cc, so each revolution it would DISPLACE 1500cc (1.5 litres), and that it’s running at 6000 rpm; that’s 100 revs per second so 50 CYCLES per second and thus, 150 litres per second @ 100% Volumetric Efficiency (VE). Think about that, a hundred and fifty litres per SECOND.
Well, given how fast that is all happening the VE isn’t going to be anything like 100%, is it, because there’s so little time to fill and empty the cylinders, right?
All the little restrictions along the way; air filter, trunking, intake silencer, throttle body, plenum chamber, intake runners, ports in the cylinder head, past the valves (which are closed for more than half of the time) and that’s just to get TO the cylinder, after all that it’s still got to get out….
SO…. what would you realistically expect the VE to be in such circumstances? Well, if you were to put a huge vacuum cleaner sucking at an unrestricted rate of 150 l/s (saving the piston’s uppy-downy motions from doing the job) pulling air through to the cylinders you’d get, perhaps 75% of the potential unrestricted flow. In that case there’s 25% of the potential flow lost to the restrictions.
You’re never going to get ZERO restriction because there’s far too much other necessary stuff in the engine and engine bay to fit filter, trunking, manifold and ports of sufficient proportions to have zero restriction.
A modern engine is pretty good out of the box and you wouldn’t ever expect as much as a 5% improvement in flow without drastic changes, and those very same drastic changes would likely make things worse in other ways. So, best ways up you might see 78 or 79% of the potential flow.
How come then, a typical modern high-performance road car engine has a VE of as much as 120%? Yes, a 3 litre engine would breathe as much as 3600cc in two revolutions!
With its silly uppy-downy pistons, pulling air past valves that are only open for typically 36% of the time, through ports that often have rough surfaces and uneven profiles, through often convoluted trunking and in from the outside world through a filter that only has open areas of a few microns. It cannot possibly be, surely? That’s over 50% more than the possible flow when the valves are only open for 36% of the time and the piston is only on the induction stroke for half of a revolution. “Get the ducking stool ready people, something isn’t right…..”
Well it can and it does, using PRESSURE WAVES. Tuning pressure waves is what it’s all about. Camshafts, exhausts, intake systems SHOULD all work absolutely together to harness the highs and lows of the pressure waves to best effect; so effective in fact that it amounts to a very significant supercharging effect.
Flow plays a very low second fiddle to pressure waves when it comes to tuning, because the difference that a loss of wave amplitude makes is far greater than the potential flow ‘increase’ from having a larger diameter and guess what? When the diameter of a pipe increases, the amplitude of the waves within it reduce because the molecule compression occurs over a greater area (the surface area, if you will, of the pipe section), so while the static flow may be imagined to be greater, the dynamic flow is actually considerably less.
For example, just look at a GT or F3 airbox - the airbox is huge to harness the pressure waves but the inlet FLOW is through a tiny little inlet restrictor, and despite this the engines still make PLENTY of power.
A flat six engine (all sixes actually for a specific reason that we don’t need to entertain here) is particularly well suited to harnessing the pressure waves that travel back and forth into, as well as across, the manifold if allowed to. They can make a huge difference to the VE at some engine speeds. This is why the (not stupid) design engineers at Porsche have gone to such great lengths to make best use of the pressure waves by employing various flaps in the system to either block or allow passage of pressure waves within the system.
When developing their engines manufacturers will do many, many hours of simulation work. After that they will make many test pieces, probably at least twenty different head casting designs, fifty camshaft profiles, piston crown designs, valve head shapes, compression ratios, manifold designs, you name it. At each engine test, a zillion sensors and probes are mounted all over the engine measuring everything that can be measured.
DO YOU NOT THINK THAT AT SOME POINT IN ALL THAT IT WOULD HAVE BECOME APPARENT TO THEM THAT IT NEEDED A BIGGER THROTTLE BODY?
No, of course not, they’re all stupid those Germans, right?
It takes Fred in his shed with probably zero engine design expertise, to think “Gad Daim, I can fit me a bigger throddle on there an’ life will be reeeeeal gewd….”
If only things were that simple…..
In the vast majority of cases BIGGER THROTTLE INTAKES DON’T WORK so save your money.
In every single Porsche case that I have EVER had on the dyno, NO bigger intake has made an improvement, and almost ALL has made less area under the curve than stock.
When a vendor selling parts says “There’s a 25 bhp difference with this Big-Boy Carlos Fandango intake Sonny Jim” just consider whether he means UP or DOWN!!!!!!
