s2kswe

I have been asking questions related to this topic for a good month now, and got some various answers. I have not found anyone with the same setup.
It all started when I contacted an experienced tuner here in Sweden and asked him if he had time to tune my car before the upcoming summer. He said sure and wanted to know some about my setup.

I told him all I had on it and then he tells me he is worried with knocking due to 2 things.
Restrictive turbine and high stock compression. (I have the .48 a/r gt3076 comin)

So I start to ask around about this and try to find a way to make my safety margins bigger. One seems to be going for a .63 a/r housing.
Another one is to directly go for E85 (102-105 octane) compared to 98 from pump fuel.
Also making the system more efficient overall would give me more HP and I might be able to settle with alittle less boost. Which also helps.

That is 3 things.

Today I was reading in a book I recently bought by recommendation from another s2k'er. It is Maximum boost by Corky Bell.
In this book I find the following picture and gets scared like shit once again.

I did plan to run 7-8psi of boost on stock compression with 98 octane from the beginning.

How accurate is this table? Should I be worried? I do not want to have mu car tuned super rich to be able to run, just makes for an inefficient system overall, and I was really looking to build something powerful yet efficient when I put money into turbo.
That table suggests 110 octane racing fuel for my level of boost and the stock compression.

gotswap

What is the print date on that book? It seems a bit out dated or a general guideline. To answer your question it will be completely safe as long as you have a good tuner, there are plenty of people running 7-psi on a stock motor including myself.

Spec_Ops2087

If all you want is 7psi 91 octane is even fine let alone 98.

Soul Coughing

I'm pretty sure the 98 in europe is comparable to 91 or 93 here. The way octane is measured in europe is different than the US!

OT:

The amount of people running that overall compression is pretty big, if you get it tuned correctly, you shouldn't have issue!

slimjim8201

Please correct me if I'm wrong. You're setup will consist of the InlinePRO turbocharger kit, the GT30R with a 0.48 A/R turbine housing and stock compression. It's almost identical to my old setup with the exception of the compression ratio...I had the 3mm gasket.

I think the 0.48 A/R turbine is perfect for a car with the 3mm gasket because it allows you to boost the daylights out of the motor with relative safety, resulting in monstrous midrange torque while still allowing for 400+ rwhp up top. The consensus here is that 10 psi is the maximum safe tune with the stock compression. Countless tuners and owners have stopped at or around 10 psi for various reasons. Some go beyond, but for the sake of this argument, lets say that is the maximum safe boost pressure.

The 0.48 A/R turbine is highly restrictive, resulting in a lot more back pressure on the engine which propogates through to the intake side, resulting in higher boost pressures necessary for a given mass flow rate and thus power level. It would be a perfect match for a highly efficient tubular manifold where the manifold design allows for lower boost pressures for a given amount of power. My setup utilized a less efficient manifold design and I compensated by reducing the compression ratio. Your setup is odd in that you have an ultra restrictive turbine housing and the less efficient manifold design coupled with high engine compression. Given the maximum safe boost level of 10 psi, you won't be able to full exploit the turbocharger, not able to boost the daylights out of it to push enough air to make reasonable power.

You can solve all a lot of potential issues and give yourself a lot of piece of mind if you lower your compression.

s2kswe

Yes Jim, your setup is the closest i have seen, the lowered compression is the difference. I agree with you that this setup seems a bit odd.
This setup was chosen on Chris recommendation tho, and maybe I should have read some more on the particular subject. As I think about it, a .63 turbine housing or even a .82 would be better.
If i have to spend more money to buy a new housing for the exhaustside what would you recommend me to? the .63 or the .82?
My feeling right now is that I will have to change it either before installation or when we realize its crap at the dyno :/

Before he quoted the items he thought would be good I told him I wanted an efficient setup and power earlier than stock. That was most important. I also told him I wanted somewhere close to 330-350rwhp.

I do plan to try to build by own tubular to replace the inline one just to raise efficiency.

@gotswap there are a picture in the book talking about a 2002 BMW engine but other than that I didn't find any newer signs. Still it cant be from the last millenium if not Corky Bell has a timemachine

@soul Here in Sweden we can buy either gas called 95 octane or gas called 98 octane if that is any help.

slimjim8201

Ah, for 330-350 whp, 10-11 psi might be just fine with that turbo selection to be honest with you. I wouldn't discount it just yet. And I would invest in a 3mm headgasket over going with a larger turbine size, particularly for your goals. I'd sacrifice 500 RPM of spool time to have a dominating mid range and a huge safety margin.

Your setup + 3mm headgasket would require like 15 pounds of boost to reach 350+ HP. It would be identical to my setup but with a lower boost level. I ran 18-19 without issues. 15 would be golden.

s2kswe

That pretty much means lower compression or change turbine housing for my needs. Cause 10-11 psi is not good for the stock compression, I can feel that. Especially with the .48 turbine housing.

This means I can either spend money to buy a new turbine housing, change to a homemade "as good as I can make tubular" remain stock comp and put 8 psi into the engine.

OR

Buy headgasket (and probably clutch) and boost abit more.


I had a plan tho, and that plan was to install the turbosystem on stock compression, have the engine to show stock emission values on idle and craft some neat factorylooking heatshields that hides much of the turbocomponents.
I have to drive my car to the car inspection next summer, and the guys up here in Middle/northern Sweden probably haven't inspected a single S2000 as there is no one else nearby.

The tests they do is just checking under the hood, making sure the battery sits tight, and just a quick glance in general. They check headlights, check for rust under the car, they check tires, wheelbearings, steering etc.

Then they drive it around the parkinglot, test brakes, park it and hook a device to the exhaust and check if the lambda value is correct. Just idling.
My intercooler will have a thin layer of flat black up front to not wake attention.

So I was really hoping to get away with just going there with a car in good condition and then just driving off approved. This is the main reason why I want stock compression. Maybe I am dreaming. One thing hit me tho, how does the air pump work thats behind the front at the left side of the car? What does it do? pump air to the exhaust? Then I might be f****d once again.

slimjim8201

There are tons of owners here pushing 10psi on stock compression. If your tune is safe, I wouldn't worry about it. "Especially with the 0.48 turbine housing". You need to stop listening to that tuner of yours. If you think you are going to hit 350 rwhp with a larger turbine housing and 7 to 8 psi, you are mistaken. It takes almost 10 psi to reach 350 rwhp with a GT35R and the Inline kit on stock compression. It will take at least that with a smaller turbo.

And whatever your selection is, it's going to be difficult to hide the fact that you have a turbo kit on your car, whether its an InlinePro setup or anything else. Not having stock compression will be the least of your worries at an inspection.

s2kswe

Ahwell, I will do like this. Since the turbo is coming, I will build the car take it to the dynoguy and let him do his job, and then I'll see where it heads. They have very good knock-listening equipment so the risk for breaking anything is minimal, also with all the experience they have.

I will see what 8 psi on this turbo can do and if I am unhappy I will have to consider that then.

Thanks for all the input.