Turbo lag... How much are we talking about?
 

I'm torn between a Turbo or a supercharger. I've read just about everything on this site about forced induction on this car, but I really don't have a good feel for the difference between the onset of power between the two modes of FI. (I worry more about this than top end because I use the car for DD and for some auto-x work.)

Some say the turbo lag is minimal and not noticeable with this car, others say the SC is the only way to go for someone with my needs.

I don't want to start a debate about which type of FI is better, but I want INPUT FROM PEOPLE WHO'VE DRIVEN BOTH. How much lag is there with a turbo and would you want to auto-x/DD with one compared to going SC...which generally means lower torque and overall HP????

Thanks, in advance, for your help.
Mark

This question has been asked time and time again.

If your turbo is small enough you can almost tune out any turbo lag. Running a small turbo will limit the maximum horsepower you can produce.

A large turbo will have lag.

A positive displacement (aka twin screw) supercharger will have instant torque but will die off in the top end.

A Centrifugal supercharger will build torque and hp all the way to your top end.


I say there are two great options for DD/auto-x if you are not looking to go into a classed competition. Centrifugal Super charger and Small turbo.

(p.s. i've driven or ridden in all four of the above on a fa20 motor.)

v1ru5.... I appreciate your response. You gave me a little of what I asked for, but didn't answer the main point of my question.

I know small turbos lag less than large ones...so I asked for folks like you who've driven both types of FI to try and give me a feel (time, butt-dyno, etc.) for how much of a lag we're talking about and then compare that to the power onset of SC. I hope this clarifies what I'm asking for.

Thanks!

Certainly a good question, no doubt, hopefully I can help.

Turbo lag, at least from the kits we install here by Full Blown, have very minimal turbo lag. The turbo utilized on this vehicle isn't a huge turbo you will see on any drag racing V8, it's a smaller turbo, something similar to what you would see from factory on an EVO 9 or 10 for example (just an example, I know they're not the same). When I drive a customers car after we've installed the kit on, I find that the turbo really starts to kick in around 2500-3000RPM, which is very very minimal in terms of lag. If a turbo kicks in at 5000RPM+, I consider that pretty terrible turbo lag. 4000RPM+ Ok Turbo lag, not terrible. Anything under 4000RPM where the turbo starts producing peak power, is very acceptable, and I wouldn't consider it any loss since most of the guys on this forum who are used to driving an FRS stock, usually drive at higher RPMS to make up for the lack of power and torque on the bottom end.

You wont find much lag on supercharger kits since it's belt driven and not driven by exhaust gasses. Twin screw superchagers do not have lag whatsoever, but typically output a ton of heat which can lead to heat soak and further issues. A lot of companies in the V8 Muscle car world use twin screws for the added torque, but most of them come with intercooler options. I don't sell any twin screws for the FRS/BRZ, but I don't believe I've seen an intercooler on any option. Centrifugal applications like Vortech, will build boost at a similar rate, just a tad quicker than the turbo, but peak power typically comes in sooner for a small turbo than it can for the centrifugal supercharger.

These are just generic claims though, this all totally depends on the tune, injectors and whatever else you've done to the car that can increase or decrease turbo lag. Obviously a less restrictive exhaust means it's easier for gasses to go through the system which effectively means, less turbo lag, BUT that's not necessarily the case with superchagers, who do see benefit for an exhaust, but it doesn't help with a faster spool, and doesn't give you as much power as it would on a turbo vehicle.

Hopefully that helps and my answer helps your decisions. We have another FBM Turbo car coming in the next 2-3 weeks for install, I should have videos for it after we're all done so you can check it out. I'll do my best to concentrate on turbo lag for you as well ;)

Something I've also wondered (which I consider very important for the FR-S), is I believe "transient throttle response" - i.e. when you are on and off the throttle.

Can the throttle also be modulated, etc. with a turbo? From what I understand it can't be nearly as good as a S/C would but I've yet to driven a turbo FR-S.

EDIT: sorry not trying to distract from OP's post I just think these are all important for a more purely feeling car

Of course it can, or the manufacturers wouldn't sell factory turbocharged cars. And conversely, if throttle modulation was as bad as s/c proponents claim, manufacturers wouldn't use turbochargers.

The problem is that it's all going to depend on your personal driving style and feelings. It's like coilovers - if you ask 10 people how they felt, you'd get 10 different opinions on the ride quality ranging from "omg they were so smooth and soft" to "that is the hardest suspension I've ever ridden on".

Well, I've also never driven a factory turbo car that I liked the feel of... in terms of good on-off throttle and pedal modulation (as well as pedal feel but that also may or may not matter...)

Honestly I don't think vendors should be commenting on a thread like this, no offense at all to you but its the nature of the beast that vendors are always going to be recommending their product over all others.

having had both a supercharger (comp tech centrifugal) and turbo setup (twinscroll gtx30r) on my old S2k, very little difference in "lag." not that the comptech had lag but the boost built through the rev range vs under load boost of the turbo, depends on the driver, if you shift down to pass your really not going to feel much lag, a PD supercharger is going to give you much better transient response at lower rpms. it will just go when you push the gas vs 1 or 2 seconds of lag with a turbo under the same situation. a properly sized turbo is going to be pretty decent though.

While I understand your sentiment, understand that I spent 10 years as a automotive photojournalist in Japan before I started work with a manufacturer, and have a lot of experience not only with driving nearly every type of vehicle, but experience in giving semi-accurate feedback on it.

I meant to type this out a bit clearer in my comment about the coilovers - the only way to really decide about acceptable lag/response/power is to personally drive the cars. Listening to others recommendations about FI/suspension/etc only tells you what they like/dislike, and will be colored by their actual driving experience.

I have a t3/t4 60 trim turbo. I believe its a bit bigger then the gt28 that modbargains is talking about. One thing Ive noticed which really is huge in this turbo lag debate is that our cars are naturally pretty high in revs when cruising. Really this all comes down to your style of driving. I tend to stay right aroud 3k all the time so when i hit the throttle I go right into boost. From my perspective this would be very little to no lag. now if your talking from a stop taking off, there is a couple seconds lag but honestly this car does not keep traction when you take off na. You def do not need to be boosting off a line. From take off I usually hit boost within a second or 2 which is darn good for the size turbo I run. Avo said it best though it really depends on you and your driving style.

As much as i love superchargers because of the nature of their behavior
people always run into belt issues which is why i would go with turbo.
I don't care what anybody says with turbos you will Always have lag.
My gti hits boost at 1800 rpm and even that low its pretty annoying. It's like you are dragging dead weight until boost kicks in.

Have you searched that new electric supercharger? It doesn't offer as much power as othe fi kits but it turns the car from the pathetic slow car it is to something respectable.

Thank you all!!! This is the type of info I needed.... and the question about throttle response didn't put this off topic at all. It was something that I should have asked about two given the nature of the info I was looking for!

meh, get both.

He didnt recommend his turbo kit.. he said that everyone has thier own opinions on things even if its the same exact product. He actually puts on good information and probably knows a bit more about turbos with his background. no need to be rude, its a forum people can have thier opinions and share thier knowledge.