Is Turbo Lag That Bad..??

solaris=amazing · 01-09-2005, 02:47 AM

I watched a show the other day on the new mitsu EVO, and the dude was saying how fast it is, which it is, i love that car. BUT, he did 30MPH and he said he had it in high gear, and some other POS car was faster then him, on a roll. He said the turbo lag was so bad.

I always liked the dodge neon SRT, and that little car has a big 4 cyl, with turbo, and i always wondered..how the hell does lag feel..?

Neutrino · 01-09-2005, 05:50 AM

Quote:

Originally Posted by solaris=amazing

I watched a show the other day on the new mitsu EVO, and the dude was saying how fast it is, which it is, i love that car. BUT, he did 30MPH and he said he had it in high gear, and some other POS car was faster then him, on a roll. He said the turbo lag was so bad.

I always liked the dodge neon SRT, and that little car has a big 4 cyl, with turbo, and i always wondered..how the hell does lag feel..?

LOL yes the infamous Clarkson, don't always take him seriously. He likes to exagerate stuff often and to make stupid jokes. His show is awesome though.

Basically what he did was, exagerate the effects of turbo lag, who in their right mind would use 6th gear to accelerate from 30mph.

Anyway most of the time turbo lag is far overexagerated, yes it exists but in most cars especially modern ones with a properly matched turbo turbines and compressors it will not be a big issue.

Also if you really think about it basically all NA cars have a "turbo lag" that never ends. Because turbo lag is is basically the NA power of the turbo engine. However this "lag" is felt more in turbo cars because they have ussually lower NA power due to a slight exaust backpresure and lower CR plus when the boost kicks in the power difference is so large that the previeous power levels seems ridiculous. In an NA car you'll never feel this difference because there is no boost to kick in so you basically don't know what you are missing

Now there is also a big difference between turbo cars as far as exibiting lag. The smaller the engine and its CR and the bigger the turbo the more lag you'll feel and viceversa. But even in the EVO for example which has only 2.0L and a pretty big turbo the lag is not that bad and the new 05 models are even better due to turbine redesign. Only if you want to push that evo to 400,500,600 hp or other huge amount requirering a huge turbo you'll have big lag issues. And even then lag will be an issue only if you are caught flat footed, but if you are ready to race you'll have that engine under load threfore spinning that turbo. Also in case of road racing only super tight corners can drop you into lag territory but there are ways to minimise that problem.

And to answer your specific question about SRT4. Lag in that car is virtually non existent. I have quite a bit of dirrent experience with this particular car and let me put it this way: it pulls like a muscle car from low rpm. Actually its full 250TQ starts as low as 2400RPM. And even with the stage 3 large turbo upgrade it still has a sick powerband.

And as they say a picture is worth a 1000 words here is the dyno sheet of a stage 3 SRT4:

just look at that TQ curve. Does this seems like a car where lag is a problem in power delivery?

PS. I hope I was clear enough, its 4 am here and i really should be slepping and nost posting while my cognitive functions are significantly impared.

solaris=amazing · 01-09-2005, 02:37 PM

Wow thanks. Yeah i love both the evo and the srt4, everyone bashes both these cars, saying like if they didn't have turbo, they'd be grandma cars..True, BUT, if muscle cars has 200hp, they'd be slow as dog shit.

I personally NEED a car with torque, especially if you hang with alot of people and all that weight get in the car. My 270ftlbs torque tbird does a decent job..

solaris=amazing · 01-09-2005, 02:39 PM

Forgot to mention, yeah, why the hell would anyone accelerate in 6th gear, at 30MPH. Lol, i can get in a 801hp Z06, in gran turismo 3 aspec, and put it in 6th, on a roll of 30mph, and it's slow as shit..

Lol, best game ever..

Andy Dorsett · 01-09-2005, 03:27 PM

I have a 96 Impala that used to be my wife's daily driver. There was a time that an 87 Grand National was my daily driver. My wife would occasionally drive the GN and hated it. She was used to the instant power of the Impala and would go to pull out into traffic. She would say "It wouldn't go and I gave it more gas and it wouldn't go so I gave it more gas and then all of a sudden it was sideways". The GN was running big turbo and 20psi of boost so it had lots of lag and when the turbo came in it more than doubled the power. In a rolling race the Impala would put a half car length on the GN and then the GN would pull away like the Impala was standing still. The more boost the more lag.

nissanfanatic · 01-09-2005, 07:34 PM

Lag is overrated. I get spool at 3500-4000rpm and I love it.

PWMAN · 01-10-2005, 06:05 PM

3500-4000 RPM??? Man you got slow spool. With the stock turbo I got full boost of 15 PSI by 2800 RPM. Now with this S70 I get full boost around 3200. And thats with a turbo thats capable of 350 WHP on a 8 valve head.

I feel bad for these Honda guys that buy full hybrid T3/T4 turbo's for their 1.8L with .82 A/R turbine housings to accomplish 250 WHP and not have full boost until 6000 RPM. I have a straight T3 turbo and getting 300 HP with an 8V head. Oh and did I mention 350 ft/lbs of torque? LOL

CBFryman · 01-10-2005, 06:26 PM

lag in a super powerful car with late boost is great. if you misshift or jsut wnat ot have fun and your boost drops and you get on it agian you are just slightly pulling and yo ucould still lean up if yo uwanted to but hten boost hits and you cant move your mouth and you are strugleing to keep your head up. thats a feeling. sort of like going up a steep incline on a rollercoaster after going down a huge high speed drop. but if a properly sized turbi is used full boost should hit by the mid 3,000's for sure. some even as low as 2,000RPM.

PWMAN · 01-10-2005, 06:50 PM

Well, if you get full boost by 2000 RPM your turbo is too small. Full boost by around 3000 RPM is good, for a bigger turbo around 3500 is good. But if you are using a stock turbo (on a factory turbo car) you should have full boost by 2500 RPM. But sometimes the ECU will limit boost until a certain RPM, in that case it does not count. I'm talking about if you are running a manual boost controller.

Andy Dorsett · 01-10-2005, 07:22 PM

A turbine housing is a compromise between full boost engine speed and top end restriction. As stated above a turbo that reaches full boost by less than 3000rpm is leaning a little in the restrictive direction and 2000rpm is way too far. Big turbos are best suited with automatics with higher stall speed convertors where the engine does not operate below 3000rpm anyway. A big turbo with a manual or factory torque convertor is a less than ideal setup.

PWMAN · 01-10-2005, 09:15 PM

I agree with your first part, but about the second part I disagree. Big turbo's are fine on manual tranny's, you can keep the RPM's up whereas unless you are running a manual valve body you are gonna shift and lower the RPM's. Auto tranny's need a smaller turbo so you can brake-torque it and come off the line like a bullet. This is better for drag racing not for the street, because with street tire's you'll never get traction. Also, a manual trans tipically has more gears, so the RPM band stays higher and you also accelerate faster. It's just off the line that suffers, but again thats not necessary for a street car.
Of course, this all hinges on what you and I consider ''big''. I consider anything full hybrid T3/T4 to be big. Right now I'm running a moderate turbo, it's a straight T3 though. A GN wheel (AKA super 70) with a .63 A/R turbine stage 1 wheel. On a 16 valve engine such as a honda the turbo is capable of 400 WHP. This is why it angers me to see turbo kits out there for honda's that come with bigger turbo's than I am running. It's absolutely stupid to run a 50-57 trim hybrid at 6-8 PSI on a honda and not have any boost until 5000 RPM. That turbo is meant to be run at 25-35 PSI levels.

Andy Dorsett · 01-10-2005, 11:44 PM

You made an important point. It all depends on what you think "big" is. My car makes 456Hp and 609lb-ft at the rear wheels. T64E @ 12psi .85AR You don't get manuals that will hold up to that. I was focusing on strait line performance. I have rear wheel drive and good tires (I consider Nittos street tires) so I can put it all down even on the street. Most high powered or what I consider high power use a transbrake to build boost at the line as you describe. For a strait line all else being equal an auto with high stall and transbrake will always beat a manual even on the street.

PWMAN · 01-11-2005, 09:28 AM

Maybe for a GN you cannot find a manual tranny to hold up to those powel levels, which I still find that hard to believe because I know a guy that dyno'd 373 WHP and 425 ft/lbs in a daytona with the 2nd strongest tranny not even the beefiest one. And I'm sure that tranny will hold more too. If Chrysler can make a bone stock FWD tranny to hold up to those power levels, well....
I have the 3rd strongest tranny in my daytona and I'm pushing 300 WHP, but thats maxxing it out.
I prefer a manual on the street because it's more fun. A manual valve body auto is cool too, but you still don't have as many gears. Also, auto tranny's will have more drivetrain loss.
From a dead stop, everything being equal the auto would probably win on the street simply because of the launch. But from a roll, different story.

nissanfanatic · 01-11-2005, 01:12 PM

Garrett T04B .69ar turbine P-Trim turbine wheel on a 2.4 DOHC. I had the late boost in mind so the car drove like it was NA in everyday driving. It is sized properly. I don't drop out of boost when shifting.

exman98 · 01-11-2005, 01:57 PM

so would a bigger turbo be worth the longer lag on a small engine?
or should smaller engines just stay away from big turbos?

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