Reducing Turbo Lag...???

[Stani1029]

what can i do to reduce the lag on my turbo?? the turbo kicks in at around 4000rpm i think, dont know if this would work but would fitting a battery powered fan that spins at 2500rpm constant to the intake side of the turbo keep the turbo spinning or is that just a stupid idea??

 

[Ed]

Only one way (that is practical) and that is fit a smaller turbo

 

[Ed]

Its not lag by the way. Its known as the boost threshold. Lag is the amount of time it takes to come on full boost whilst it is in an area of operation in which it can do so. I.e. your at 6000 rpm no throttle you floor it and the boost builds, how long that takes is turbo lag.

 

[Retepetsir]

Your turbo is massive for the size of the engine, so as Ed says ideally you'll want to downgrade.

 

[Stani1029]

Its not lag by the way. Its known as the boost threshold. Lag is the amount of time it takes to come on full boost whilst it is in an area of operation in which it can do so. I.e. your at 6000 rpm no throttle you floor it and the boost builds, how long that takes is turbo lag.

yeah but when i put my foot down at about 6000rpm there is no "boost threshold" only lower down the rev range that it happens, what size turbo would someone recommend for the size flange that i have??

 

[COZ!!!!]

You can get some turbo insulation that reduces lag by 500 rpm apparentley. I read it in redline magazine. Also helps alot with under bonnet temps. As we all know turbos produced alot of heat

http://www.nimbusmotorsport.com/ProdShop2.asp?id=663&CATID=282

 

[Ed]

I have cleaned this thread up a bit (soft delete) since I want it to remain factual.

Turbo insulation is a good idea. The best method is to ceramic coat the turbine housing and exhaust. Turbos actually don't produce any heat. They actually make use of the heat they are subjected, which would otherwise be mostly wasted. The heat from the turbo and exhaust is wasted energy being produced by the engine. As it still has a lot of energy within it this drives the turbo.

You could see this by measuring the heat and pressure before and after the turbo. Its a really big difference.

yeah but when i put my foot down at about 6000rpm there is no "boost threshold" only lower down the rev range that it happens

That's exactly my point. At 6000 rpm you are above the boost threshold so lag is very small. Below this and you are and the turbo then is very unresponsive. Hence why you need a smaller turbo to bring the boost threshold down to about 3500 rpm.

 

[Craig]

Could you not open the wastegate slightly so that some of the restirction posed by the turbine blades is bypassed?

 

[Antony]

this would only make it worse.

if it takes X amount of energy to spin the compressor upto a certain Pressure, releasing some of that energy before it has done its job will only reduse its effectiveness.

what you need is for the energy that is being utilised to turn the turbine wheel to directly increase the energy being released by the compressor wheel only at a lower over all speed. its all about gasses, the volume of exhaust gasses being exhausted from a CG13 engine is vastly smaller than that of an SR20DET for example.
an sr20 can exert the same amount of energy per revolution as a cg13 can for every 2 revolutions (roughly) regardless of how much air is being flowed into the engine, the very fact that the exhaust gasses are exiting the engine at a volumetric pressure vastly greater than a cg13 engine gives you some idea of how much the little cg13 has to work to turn the turbine blades of a turbo designed to work with the SR20 or similar sized engine. thus taking much longer to do so, hence the Threshold or "lag" that stani is encountering.

the only way to overcome this is to fit a smaller turbo, a turbo that needs much less gasses / energy to actualy spin the compressor wheel. this way the speed at which the
CG13 is effective (the threshold) is lowered and the turbo will come on boost much faster.

that said, if you put a T15 turbo on an SR20 engine for example, it would not only be vastly under sized but may actually cause a restriction due to its inability to flow enough air through the compressor housing.

So in summary a smaller turbo is the answer.

 

[Baz]

Could you not open the wastegate slightly so that some of the restirction posed by the turbine blades is bypassed?

That would make things worst as stated, I had the wastegate actuator C clip come off a starlet turbo and ended up holding the wastegate open the thing did'nrt boost until 5000rpm, the longer you can keep the wastegate closed the better,without over boosting off coarse.

An electronic boost controller or an uprated ajustable actuator or both would do the job.

Turbo sizing obviously has a big part to play,matching a turbo to the engine capacity and to still do the job you need it to do and supply the boost you want safely

 

[Ed]

Had a Starlet on the dyno today and its wastegate opened under boost - even with the actuator pipe disconnected. It made poor power as a result, and needs a stronger actuator.