Turbo lag question.

rnoswal · 02-10-2006, 03:14 PM

I am curious about turbo lag. My car has the stock turbo and everything else but a larger 3' exhaust system. If I rev the heck out of the engine and shift quickly I can keep the lag at almost tolerable levels, but just moderate shifting, the lag is about 2 seconds before spooling up again. I had always thought it was a matter of the stock turbo being too small for large HP gains, but I thought the smaller turbo meant quicker spooling up times and less lag. Unless the exhaust hurt that part of it. I bought the car with the large exhaust on it so I have nothing to compare with before and after.

It has the stock elbow from the turbo and I know that is somewhat restrictive, but again is a large lag time normal? The car came with another turbo boost guage on the pillar and seems to mimic the stock guage pretty well. The wastegate/bov seems to be working well. The manifold pressure is around -15 to 0 psi under normal driving conditions before I want to use the turbo. On the freeway in 5th gear it really accelerates nice and very strong under booste, no problem with turbo lag there.................but if I down shifted, that is another story. Lost manifold pressure and then the time to catch back up again.

Any help is appreciated.

Russ

TONY! · 02-10-2006, 10:18 PM

It is hard to answer you specifically because you seem to have answered your own questions, and so I am confused as to what you are asking.

Here are the facts though.

Larger turbos have more lag time than smaller ones.

Larger turbos have more potential to make lots of horsepower than smaller ones--if the engine can put out enough exhaust pressure/volume to work the larger turbos.

The less backpressure you have with your exhaust, the less lag time you will have, but you can't avoid lag by eliminating your exhaust either.
Keep in mind that the turbine will spin when there is a variation in pressure: in an extreme example, if you had lots of pressure in your exhaust and the same pressure in you manifold, the turbo would not spin. The greater the difference in pressure before and after the turbine, the quicker the turbine will spin. Freeing up exhaust pressure helps get the turbo to spin quicker in that sense.

ryemann32 · 02-11-2006, 03:23 AM

i just bought my new supra last week and pull the stock elbow off what a piece of junk restrictive siverly buy yourself a good downpipe and run 3in or bigger and i think your problem will be solved i have a full 3in back from my old girl and what a diffrence in cars can t wait to see the diffrence in the new car

rnoswal · 02-11-2006, 04:48 AM

I know you are right about the elbow being restrictive and I am going to replace it as soon as I can.

Mainly I was just curious about the newer turbos and if the lag time had been reduced noticably. I would think after almost 20 years from my 87 that technology would have improved the turbines so it would spool up faster and come in a little earlier.

I guess I really notice the difference between a hot and cold engine. The power seems to really come on strong cold but takes longer after it warms up. The ambient air temp is still pretty cool though, so far anyway.

I have seen the aftermarket elbows somewhere but can't remember where. Any direction there please.

Thanks
Russ

ryemann32 · 02-11-2006, 10:16 AM

a new down pipe is the only way to go get rid of elbow if u are running a stock turbo order a downpipe from a company called cooleeze i have one and it rocks
we also live close to each other and i ended up being his powdercoater for all his ic pipes check out his site he specializes in supra parts high quality and great service

ComptonsF1NEST · 02-12-2006, 04:45 AM

ball bearing t4 GT sereis by garrett will help u a hell of a lot.

Also Increasing ur Intake capabilites (the more air in the more air out) such as
TB, IM, etc. Also the Intake on the turbo. Try just putting a screen on the inlet of the compressor

rnoswal · 02-12-2006, 05:42 AM

Why the screen, to keep out stuff or cause turbulance with the incoming air flow? I might just try to take the elbow off and either try to make something or grind it out for now. I was also curious about the downpipe from cooleeze, if I upgrade to a better and bigger turbo, will it fit that too?

Russ

02-10-2006, 03:14 PM	#1
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	Turbo lag question. I am curious about turbo lag. My car has the stock turbo and everything else but a larger 3' exhaust system. If I rev the heck out of the engine and shift quickly I can keep the lag at almost tolerable levels, but just moderate shifting, the lag is about 2 seconds before spooling up again. I had always thought it was a matter of the stock turbo being too small for large HP gains, but I thought the smaller turbo meant quicker spooling up times and less lag. Unless the exhaust hurt that part of it. I bought the car with the large exhaust on it so I have nothing to compare with before and after. It has the stock elbow from the turbo and I know that is somewhat restrictive, but again is a large lag time normal? The car came with another turbo boost guage on the pillar and seems to mimic the stock guage pretty well. The wastegate/bov seems to be working well. The manifold pressure is around -15 to 0 psi under normal driving conditions before I want to use the turbo. On the freeway in 5th gear it really accelerates nice and very strong under booste, no problem with turbo lag there.................but if I down shifted, that is another story. Lost manifold pressure and then the time to catch back up again. Any help is appreciated. Russ

02-10-2006, 10:18 PM	#2
TONY! 12psi boost Join Date: Sep 2005 Location: Troy, NY 12180 Posts: 353	It is hard to answer you specifically because you seem to have answered your own questions, and so I am confused as to what you are asking. Here are the facts though. Larger turbos have more lag time than smaller ones. Larger turbos have more potential to make lots of horsepower than smaller ones--if the engine can put out enough exhaust pressure/volume to work the larger turbos. The less backpressure you have with your exhaust, the less lag time you will have, but you can't avoid lag by eliminating your exhaust either. Keep in mind that the turbine will spin when there is a variation in pressure: in an extreme example, if you had lots of pressure in your exhaust and the same pressure in you manifold, the turbo would not spin. The greater the difference in pressure before and after the turbine, the quicker the turbine will spin. Freeing up exhaust pressure helps get the turbo to spin quicker in that sense. __________________ -------------> ITEMS THAT ARE STILL AVAILABLE FROM AN '88 PART OUT <------------- _____\|_____ /. . . \ . . . \ . .\ ( ]/ . . . . \ . . . \ . .\[ ) _________________ /OO]====(W)====[OO\ [___________________] [ [O] ///______\\\ [O]_] ____________________[\|\|]______________[\|\|]____________________

02-11-2006, 03:23 AM	#3
ryemann32 3" Exhaust Join Date: Nov 2005 Location: surrey bc canada Posts: 102	get rid of stock elbow i just bought my new supra last week and pull the stock elbow off what a piece of junk restrictive siverly buy yourself a good downpipe and run 3in or bigger and i think your problem will be solved i have a full 3in back from my old girl and what a diffrence in cars can t wait to see the diffrence in the new car

02-11-2006, 10:16 AM	#5
ryemann32 3" Exhaust Join Date: Nov 2005 Location: surrey bc canada Posts: 102	buy a new down pipe a new down pipe is the only way to go get rid of elbow if u are running a stock turbo order a downpipe from a company called cooleeze i have one and it rocks we also live close to each other and i ended up being his powdercoater for all his ic pipes check out his site he specializes in supra parts high quality and great service

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02-11-2006, 04:48 AM	#4
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	I know you are right about the elbow being restrictive and I am going to replace it as soon as I can. Mainly I was just curious about the newer turbos and if the lag time had been reduced noticably. I would think after almost 20 years from my 87 that technology would have improved the turbines so it would spool up faster and come in a little earlier. I guess I really notice the difference between a hot and cold engine. The power seems to really come on strong cold but takes longer after it warms up. The ambient air temp is still pretty cool though, so far anyway. I have seen the aftermarket elbows somewhere but can't remember where. Any direction there please. Thanks Russ

02-12-2006, 04:45 AM	#6
ComptonsF1NEST Stock Join Date: Feb 2006 Posts: 3	ball bearing t4 GT sereis by garrett will help u a hell of a lot. Also Increasing ur Intake capabilites (the more air in the more air out) such as TB, IM, etc. Also the Intake on the turbo. Try just putting a screen on the inlet of the compressor

02-12-2006, 05:42 AM	#7
rnoswal Lexus & 550's Join Date: Apr 2005 Location: Bossier City LA Posts: 556	Why the screen, to keep out stuff or cause turbulance with the incoming air flow? I might just try to take the elbow off and either try to make something or grind it out for now. I was also curious about the downpipe from cooleeze, if I upgrade to a better and bigger turbo, will it fit that too? Russ