Turbo lag?????

[snwman77]

What causes turbo lag!!!
Is it a lack of intake air or is it too much back pressure at the turbo???
Has anyone ever takin off the intake and run the sled or takin off the turbo and put a stock pipe and can back on too see what the causes the turbo leg.
Or is it the wrong air fuel ratio.
I would like to know what some of you guys have seen causes most of the turbo lag.
I would like to get more brap brap out of my turbo M1000.
Some guys will want me to change up my clutching but I feel its a little lean on the bottem end just before the sled comes onto boost. The sled is runs very nice right now, but like I said, I want more Brap brap.

(Edit, I spelt leg lag)

 

[ippielb]

All turbos will LAG off the start, because it needs to start spinning the turbine. That's the price you pay. Good thing about aerocharger is that it has variable vane turbo's.

 

[ACMtnCat]

I get turbo leg when I climb a gnarly chute that has no turn out. When I make it to the top my right leg shakes a bit. Thats what causes my turbo leg!

 

[snwman77]

I get turbo leg when I climb a gnarly chute that has no turn out. When I make it to the top my right leg shakes a bit. Thats what causes my turbo leg!

CLAP CLAP ClAP good answer good answer!!!

 

[dogtownbutcher]

I too ride a TM1000 and when i first got it , it did have the lag that you talk about... I played with the clutching and it was night and day, but i still think with the 1000 you will always have a bit more turbo lag... just my opinion..

 

[nyberg_]

what causes turbo LAG, well a ****load of different thing. big turbos with big impellers or just old stone age turbos, wrong ignition timing, backpressure in exhaustpipe, how the cylinderporting and pipe works with a turbo application. and then some

 

[Boyko]

You will build pressure in you exhaust pipe before you make boost, about 2to3 psi. Once your motor is buzzed up it is not so noticeable because it builds quickly. Depending on how much you heat up your intake charge up it takes about 20 - 25hp to make 10 psi boost on a m8. With Good tuning, fuel and clutching lag is not that big of a problem

 

[snwman77]

So turbo leg lag starts with the exhaust not getting out, not the lack of intake air.
I want to better understand the cause so i can get things just right.

 

[skudmissle]

What helix angle are u running?

 

[ippielb]

That's correct, exhaust has to go through the turbo to spin the turbine to compress air. And it takes power to spin the turbine. Engine has to work to get exhaust out. Until the turbine spins which compresses air into the engine which pushes a lot more exhaust out. As stated above you will need to wok your clutching around the lag, to try and minimize the effects. But you can't focus on just bottom end, you don't want your sled to fall on its face at top end.

 

[Boyko]

So turbo leg lag starts with the exhaust not getting out, not the lack of intake air.
I want to better understand the cause so i can get things just right.

That is were it starts.

On most systems you have to remove fuel on the bottom end because the exhaust is restricted. It is not so much as the intake being stuffed up. If you run a matching boost gauge in your exhaust before the turbo, the lag really becomes quite illustrated. It is also an excellent way to tell how efficient your turbo system is.

 

[428PONY]

As just put fuel has to be removed from the bottom end. The best solution is to drop fuel pressure and tune accordingly. A rich mixture takes the snap out of throttle. Make it it lean and mean. I run down out 35 psi and it is real crisp. my .02

 

[Dogmeat]

I've kept my stock fuel pressure (has the BD tuning board though) and removed a pretty significant amount of fuel on my 3,000 rpm setting on the BD box ... gotta figure, you're adding quite a bit of restriction to the stock tune before the turbo spools up, so thats why a lot of turbos sputter from the 'basic' stock tune you get from the builder .... I know the BD M8 kits are this way for sure ... I helped a buddy tune his HM turbo on his assault last year and it was the same way, we had to back a little fuel out of it on the low end.

 

[snwman77]

So as of now you guys agree that the turbo is restricting flow out of the engine and is the cause of turbo lag. So way did guys take the large inercoolers off to help there sleds run better a couple years back? I agree with you guys that the turbo is restricting exhaust flow and getting your fueling right will help a lot to get a nice snappy sled. Did any of you see a change on your AF gauge when you got you bottom end right ? My sleds AF gauge always reads lean until the sled builds boost, then it runs just right.

 

[wrench2race]

As your o2 sensor gets more use on it, it gets less sensitive and needs a larger amount of exhaust going through it to display an honest reading, a new o2 would probabaly help with the lean reading at low throttle/rpm. It did on mine. Yours is probably lying a little bit.

 

[snwman77]

I have a new AF gauge in the box ready to put on. I will give it a try.

 

[Wheel House Motorsports]

turbo lag isnt from just the turbocharger, but the whole turbo system. you have to look at it from front to back. the parts all have to be working together to help make it run spot on. lets start from the front.

air intake, you need a large diameter short turbo inlet, any restrictions here mean the turbo is running at a higher pressure ratio=higher charge temps at the same boost. also the colder the air the better you are. how warm it gets is just an equation, and the higher you start, well it doesnt help.

turbo sizing, i have my own theories on sizing but it needs to be close to the correct size to flow the proper amount of air on intake AND exhaust sides.

charge tube/airbox, they need to provide the airflow your motor needs, no sharp bends, tiny kinked pipes. also when off boost your turbo isnt feeding much air at all, so just like stock you need to have a rather large airbox to accomodate the fact that the vaccum spike when you whack the throttle needs the air for the motor, without this you starve it and your going to get "lag"

motor, we all stay stock mostly, obviously the porting, head, etc could be changed to better suite but im not expert there so i will leave it alone.

turbo inlet and turbine sizing. the tuned pipe on the sled is needed, but the second you reach stinger diameter there is no reason to make extra bends, have more length etc, you just loose drive pressure resulting in poor spool. I prefer a larger turbine wheel with a tighter housing to a small wheel with an open housing, combined with an external wastegate ideally. this allows for quick spool on the bottom end but a way to easily relive heat and pressure while on boost keep boost/exh pressure well balanced.

and lastly, downpipe. one the exhaust gas has exited the turbo outlet, we DONT need it, get it out of the way as quickly as possible in a pipe far greater then the turbo inlet, the greater pressure differential you can great across the exhaust wheel the better your spool.

more thoughts later....

 

[Arctic Thunder]

Doesn't the AR rating on the turbo make a difference also?

If it is to tight it can't draw/flow enough past the turbo at low RPM's. But when the turbo is spooled up it will push a lot more than you need so the clearance doesn't need to be super tight.

so an AR of .86 is open enough to flow but tight enough to build good boost.

Like ski-doonin it said, it is a delicate balance between intake, turbo, exhaust, turbo sizing, AR ratio's, full management, port timing, head clearance, fuel, etc. (thus the reason I purchased a tried and true twisted kit)

Thunder

 

[WyoBoy1000]

I say it all depends on what you have, so what do you have. answer these???

turbo
clutching
charge tube/box/IC (version)
controller (version)
reeds
exhaust
fuel system
elevation
fuel mix or ratio

BD is one of my least fav but a friend had a pg on a 09 and it didn't have much lag at all, it came out of the hole with a lot of torque, from a died stop at the bottom of a hill I couldn't pull him at all, on the flat it just depended on who hooked up and then he was gone. it had its issue but once bd them selves did some tuning on it with a certain clutch setup it was a blast to ride in tight trees and creek drainage's. With that said the right system with the right turbo will kill that one.

 

[HOOCH256]

I for one don't think there is near the amount of lag in these 2s sleds as you get in a 4s car! I know not apples to apples just saying that I've seen some cars with big turbos making huge hp #s but lag so bad they could be beat by a toyota prius! Top Gear did a pretty funny test where they raced a lancer making over 550hp Vs a Toyota prius, the race was from 30 or 45mph and they were both put in there top gears and the prius smokes the lancer too 110mph. But like skidoinit said there are a lot of variables involved but I feel the biggest contributor to "turbo lag" is improper turbo size


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