Truth about turbo positioning

[_debo]

Originally Posted by Kodename47

Mark is the guy to speak to there, I know him well. Wouldn't recommend anywhere else if I'm honest, anything that I don't do myself gets done there. I know he was looking at a turbo kit, he's done mostly SC cars as they are official Sprintex and Harrop retailers and he's tuned HKS and Cossie kits too.

I believe it may have been the Treadstone turbo kit, I haven't spoken to him in a while.

Fensport will probably try and talk you into an Avo kit as they've done a fair few now, was pretty much the only kit on the market here for ages.

I will definitely try to have a chat with Abbey then and see what they can do; as per fensport I'll pass, I really can't make myself like the AVO kit. Thanks a lot for all the previous infos, appreciated.

Originally Posted by Bfranklyn86

Thinking back to when Abbey did my car, I *think* I remember Mark saying it was a greddy turbo he had done.

I can back up what kodename has said in recommending Abbey - I've had good service from them.

That's a very valuable confirmation, thanks. Also yes, my current setup is around 250bhp flywheel so I'm looking to step up to 300/350.

Originally Posted by jsimon7777

You should just look at the kits available for RHD cars and then see what people say about them. Superchargers are more linear and probably better for a track car. Turbos deliver tons of low-end torque, though not typically with the same precision. There's also lag. As for turbo placement, there are happy people with turbos in all sorts of places. It's more about the engineering of the individual kits. You can have crap and you can have gold in every position.

Which is what I am doing but there is not that much available unfortunately, for some weird reasons it seems like the RHD markets went full throttle on SC when it comes to forced induction.

As per the SC/TC comparison, first of all I agree with @Bfranklyn86 but also, in my personal and humble opinon both FI systems can equally find their place in track/road applications interchangeably depending on the situation. And the "myth" of the turbo lag, well, it's just that a myth if we talk about properly done road application. Not that it doesn't exists but again it depepends by the way the FI is designed, in fact, if you look at most OEM solutions the lag is neglegible (at least in what I drove so far) and definitely something you can totally leave with and I talk from the experience I have with my current car.

[EAGLE5]

There are reasons so many small to medium OEM engines use turbos and big engines use superchargers. I cannot think of a single OEM flat engine that is supercharged, only turbocharged. Maybe in history there are some.

But I don't really care, to be honest. Just look at the torque curves. Get what appeals and is built with quality.

[_debo]

Originally Posted by jsimon7777

There are reasons so many small to medium OEM engines use turbos and big engines use superchargers. I cannot think of a single OEM flat engine that is supercharged, only turbocharged. Maybe in history there are some.

But I don't really care, to be honest. Just look at the torque curves. Get what appeals and is built with quality.

Indeed my mind on that is already settled, not only because of history, but also because of personal preference and that has to be TC. The issue is find the least crap kit out there, there is so little in the RHD side of the market, if I could drive LHD I would blindly go for Ptuning, but nope I can't :-)

[gtengr]

Originally Posted by Bfranklyn86

I'm afraid I don't agree with this. The positive displacement superchargers have power available anywhere in the rev range which is what you want for the road. I think a massive torque surge from a turbo is not ideal for the road unless you significantly increase the grip on this thing.

Isn't the PD blower worse in this regard? I thought PD boost hits near instantly, while a turbo takes a split second to build up. Depends on the magnitude as well, but just referring to the initial hit.

[_debo]

Originally Posted by gtengr

Isn't the PD blower worse in this regard? I thought PD boost hits near instantly, while a turbo takes a split second to build up. Depends on the magnitude as well, but just referring to the initial hit.

My understanding for what I read so far is that, yes you are correct it is instant but it is also aligned with the original behaviour of the engine and proportional to it, in other words with a supercharger is simply like having a bigger engine of the same type and behaviour, or at least this my understanding, happy to be corrected if not. With a turbo instead there is no direct coupling with the engine because turbo is exhaust driven so it's less predictable and less linear.

For what I could gather so far my take would be, pinch of salt please, if you have a big engine with natural high torque like a V8 go SC otherwise TC.

Again, happy to be corrected, because I am no expert at all just someone who is trying to learn as he goes

[Tokay444]

I need to chime in on that last one.
If you can read a compressor map, you can predict a turbo.

[Bfranklyn86]

Originally Posted by gtengr

Isn't the PD blower worse in this regard? I thought PD boost hits near instantly, while a turbo takes a split second to build up. Depends on the magnitude as well, but just referring to the initial hit.

Yeh it is instant, which is why I love it, but it is also proportional. Proportional to where you are in the rev range.

I'm no expert, but maybe larger engined OEM applications use a supercharger because the power needed to spin the blower is less as a percentage of overall engine power, making the more favourable driving characteristics worth the efficiency sacrifice overall.

P.s not trying to start any arguments here, just giving my own opinions.

[bfrank1972]

Turbos are typically 'less predictable' to drive because you have something that's not directly correlated to your throttle input changing your torque output. In most cases where a kit is well engineered (i.e. OEM stuff) that turbo lag is minimized, and also in most of those cases your power output is not at the level where the differential between on and off boost makes things dangerous or unpredictable. Also the feel is different - no matter how well engineered the turbo system is, it will never have that super crisp throttle tip in feeling that a NA or well engineered supercharger system has. OEM most often use turbos because ultimately they're much more efficient (mostly fuel economy) overall and the whole package can be precisely engineered (think large teams of really smart people and big budgets) to optimize everything. Much less easy to do this with an aftermarket kit, as those guys (small teams of really smart people, small budgets, one arm tied behind their backs) need to work with what the car manufacturer has provided. Superchargers make this somewhat easier - centrifugal units can get close (but not quite) to the power output of a turbo at their peak, are easy to package, can have great throttle response, but lack mid-range torque. PD are tougher to package, less efficient (thought they've been optimized pretty well, i.e. Easton TVS), have great throttle response, and really nice mid range torque. There's a reason each type of kit exists in the world

P.S. only reason I can see that an OEM manufacturer would use a PD blower on a large displacement motor is they're trying to produce something ridonculous, like AMG, Dodge Hellcat, ZR1, etc.

[Tokay444]

Superchargers impart immense amounts of parasitic loss, which is the reason they're not seen on smaller displacement motors that don't have the power to lose before making it back.
Twin charging however, is quite popular on smaller motors.

[PandaSPUR]

Originally Posted by Tokay444

Superchargers impart immense amounts of parasitic loss

[Tokay444]

Originally Posted by PandaSPUR

I've driven cars where it took 200 hp JUST to drive the blower...

[gtengr]

In my unscientific opinion based on looking at forum dyno graphs, a supercharger costs ~40 hp over a turbo on the 86 at similar boost levels (~<10psi).

[bfrank1972]

Originally Posted by gtengr

In my unscientific opinion based on looking at forum dyno graphs, a supercharger costs ~40 hp over a turbo on the 86 at similar boost levels (~<10psi).

Yeah that's really hard to compare - it will depend a lot on dyno, conditions, supercharger type, turbo size, tune, intercooler size, etc. Keep in mind, most turbo systems have a decent custom header without a cat, so you'd also have to compare apples to apples there as well. The closest thing I can think of is the Works turbo kit which uses the stock manifold and a smaller/responsive turbo - if you take a look at those dynos (the intercooled version) it's pretty close to being in-line with the current supercharger offerings. Even then, it's apples to oranges - they're too different. My advice to anyone shopping across both, is to try to get a little seat time in each. Positive displacement superchargers, centrifugal superchargers, and various turbo kits will all feel different, often it's more of a matter of preference instead of overall efficiency when deciding on aftermarket FI kits for our cars.

[_debo]

Originally Posted by bfrank1972

Yeah that's really hard to compare - it will depend a lot on dyno, conditions, supercharger type, turbo size, tune, intercooler size, etc. Keep in mind, most turbo systems have a decent custom header without a cat, so you'd also have to compare apples to apples there as well. The closest thing I can think of is the Works turbo kit which uses the stock manifold and a smaller/responsive turbo - if you take a look at those dynos (the intercooled version) it's pretty close to being in-line with the current supercharger offerings. Even then, it's apples to oranges - they're too different. My advice to anyone shopping across both, is to try to get a little seat time in each. Positive displacement superchargers, centrifugal superchargers, and various turbo kits will all feel different, often it's more of a matter of preference instead of overall efficiency when deciding on aftermarket FI kits for our cars.

The problem is that there is not much of a choice for us unfortunate to live in a RHD country when it comes to turbo