cheap alternative to janspeed manifold

[frank]

hi all
after 6 years and 80000 mls my janspeed manifold had aquired a few rot holes so had to come off, i couldnt justify another 200 quid so had a look at trying to improve the factory jobbie
the 4 branches are a half decent size and shape but where they join at the neck is very constrianed (20mmx40mm minus the lamda probe) which is smaller than the downpipe, in a place where the 4 exhaust pulses are fighting each other for space
its the only part that shows heat discolouration
so i cut that section out and replaced it with a length of heavy steel tube 60mm dia, squashed to shape and arc welded together
this setup has given the car very simular power characteristics to the janspeed (same bottom + midrange with a mad surge at 5000 to7000 rpm) but without the rasp and a guaranteed emissions pass
ps this might not apply to a 1.3 because when the janspeed was fitted to my super s the powerband was dead straight (more rpm=more power) with no surge at 5000

frank

 

[superls]

pics

 

[frank]

post a pic tomorrow

i,ve tried all sorts to smooth out the power curve, i,ve moved the dizzy back and forth and advanced the cams 10 deg but its still there
i dont think its a fueling problem because its still there if i,m running on petrol or lpg, and the gas feed is highly adjustable also there,s a multimeter fixed on my dash, wired to the lamda sensor which gives me the air/fuel ratio on the fly
so i think i,ll have to live with it

btw i get 270 mls / 10 quid of gas (thats cheep motoring eh!)

frank from brum

 

[rlees85]

so how much would you charge someone for a diy manifold? i know im being cheeky by askin this straight away but i cant find a janspeed anywhere :/

 

[frank]

pic (hope the link works- bit new to this posting lark)

rlees85 your welcome to my old janspeed (the rusty bit is at the bottom by the sump) ,i work near tamworth if,s thats any help

frank

 

[sonic]

you just arc welded it together then, how strong is the weld to the cast headers ? I take it that the part on the left shows the restriction in the standard manifold ? and that 60mm heavy steel tubing, scaffolding tube ?

 

[frank]

sonic

i find with cast iron, if you butt weld it together, grind it flat then run a half inch wide weld ontop "its goin nowere"
the tube was an offcut (local fabrication shop), i bit bigger than a scaf but same guage

frank

 

[sonic]

I think I'll have a go at that in the week.

 

[rlees85]

is the janspeed about fubard tho?

 

[frank]

sonic

its best to lie the manifold flat on a piece of ply and chalk all round it before you cut it up, so as the downpipe lines up ok after.
also i did a fair bit of die grinding up the ports while i could get at them

frank

 

[Soixantaine]

Outstanding!

Outstanding, Frank. To me, that's what this site is all about: a really useful bit of technical input that many of us will be interested in.

There is a chap named Harvey (retired F1 mechanic, I think, and I need to do a search) who does a little exhaust fabrication in his spare time. I have been thinking of calling him to see if he could come up with a new header where all four pipes converged into the primary cat much like you have done. Will probably try your way first, however, so it's back to the scrapyard to scrounge up a spare manifold.

S

 

[frank]

thanks soixantaine

another cheep tweek that worked a treet on my super s was to increase the pressure in the fuel rail
i took the pressure release valve off and squashed the top of the casing down in a vise, using an old socket with a slot cut in the side to clear the bent pipe
you should end up with a 2mm dome in the top which pushes the spring down harder
if you connect the prv to a spraybooth air regulator and slowly increase it you will hear when valve starts to open (35psi before-50psi after)
the fuel pump pushes out 75psi but anything over 35psi is returned to the tank by the prv
i think this mod stops the 1.3 from leaning out at high revs (mine felt quicker anyway)

frank
l

 

[Antony]

/\... i just un-coupled my lambda sensor..lol...... seamed to do the same thing.. smoothed out power delivery...

may give that a try, or just wait for a re-map and TB's

 

[frank]

antony

disregard the slot in the socket, that vacuum pipe is in fact straight! (i was getting confused with a mates rover we did)
btw the rover ones come with different settings it,s stamped on the casing (2.5bar /3 bar etc)
other mods to my super s were a ported and polished head with a 2mm skim (a bit of a waste of time really) you can,t improve much on a modern 16v head i think!
the flywheel was lightened with a serious skim and a load of 1 inch holes,
that was impressive! it had the throttle response akin to a m/bike but you feel a right nob when you keep stalling the car
also the mid exhaust pipe was altered at the flange by the second cat (exitting a 70mm apperture and hitting a flat plate with a 30mm hole in the middle can,t be good for gasflow surely)
if i do it to my current car i think i will junk the second cat (it does,nt get hot enough to work properly anyway) and extend the middle pipe then bolt the flanges together

frank

 

[Antony]

i have replaced my second cat with a metal cat, and it seems to be working ok.. doesnt need to get that hot to work perfectly..

and yeah, ill give it a try.. cant hurt if i do it on a scrappy jobee..

the only part of my system that is origonal is the bolts for the manifold..lol

i may modify the 2-1 collector on my manifold with thicker tubing and a slightly less "crushed" design...may get rid of the rasp then...

 

[frank]

just fueled my misses car up, it,s 1.0 with 1.3 cams as well but it aint got half the top end as mine!
either that manifold has added 10 hp or else her car is poorly, its so hard to tell!!
why can,t someone build a rolling road like a petrol station, where you just turn up and drive onto the rollers then thrash it in 1st and 2nd and then pull up at the kiosk to pay your 10 quid for the printout
thats the only way the average joe,s of us could accurately test any mod we,ve done

frank

 

[LastVenue]

frank

any chance of making one for any members interested? can provide a standard manifold and cover your costs.

 

[frank]

last venue

don,t mind doing yours if you want,your not far from me (and a 2nd opinion would be useful)
but can,t be arsed to do a batch of them

gotta log out now we got a 3 hr enduro on tonite

frank

 

[LastVenue]

Thats great. Let me know where to send my manifold. Can PM me at lastvenue'at'hotmail.com

 

[frank]

last venue

pm sent dude

frank