Hey guys,

I'm having an argument with a friend of mine. I think that an SR20DE would be better to turbo, because of it's naturally higher compression ratio. Running 98 Octane gas, and a good fuel and ignition management system means that you don't need to lower compression anymore. Heck, I'm going to be running 7 pounds at 11:1 compression on my car soon.

He thinks that the SR20DET is better, because it has equipment that the SR20 doesn't have, like quad throttle bodies and some other things that I forgot. He reckons these will compensate for the lower compression, not to mention that you can run slightly higher boost.

I'm thinking that even though it's true you can run higher boost on lower compression motors, you get less horsepower per pound. For example...

Let's just say a 10:1 motor makes 100 horse power per litre displacement. A 9:1 motor makes 90 horse power per litre displacement. (Fabricated numbers) So in a 2 litre engine, you make 200hp and 180hp respectively.

If you boost both of them at 1 bar (14.7 psi), you're doubling the amount of air into the cylinders, so theoretically, you should get 400hp out of the 10:1 engine and 360hp out of 9:1 engine. (This is assuming a lossless engine, which is unrealistic)

So to get the last 40hp, you'd need to keep increasing boost. Say by about 12%, so you'd need to run just over 16 pounds boost to get the same power.

By increasing max boost, you're going to increase turbo lag and so forth and since there's spooling time, also most power is coming at peak, not lower...

So even if you could run the extra boost to match the power, you're sacraficing power under the curve, meaning a slower car off the mark.

What do you guys think?

i think only the gti-r det has itb

You did not calculate the BOOM factor.

The reason Turbo engines come with lower compression pistons, is for protection. High compression engines can take boost, but not too much.

You see, unless you want to run race gas everyday, High boost and high compression pistons, is NOT a good mix.

Originally posted by spicez
You did not calculate the BOOM factor.

The reason Turbo engines come with lower compression pistons, is for protection. High compression engines can take boost, but not too much.

You see, unless you want to run race gas everyday, High boost and high compression pistons, is NOT a good mix.

Umm, I'm pretty sure I mentioned that low compression motors can take bigger boost.

What's high boost by your definition? 1/2 a bar, 1 bar? 2 bar?

You know what, my bad you did mentione it in a way.

Thing is the SR20DET does have things the DE does not which makes it a better choice in the long run :

Here are the differences between the DET and the DE:

The DET has oil squirter piston coolers
The DET has a bigger oil pump.
The DET has a different front pulley.
The DET has lower compression pistons (8.3:1 vs 9.5:1).
The DET has bigger injectors.
The DET has direct ignition.
The DET has a variable intake cam, runs retarded at idle, advanced mid range and retarded top end.
The DET has mechanical shim in bucket type lifters with a slightly bigger in duration exhaust cam.

The GTi-R DET has individual Throttle body injection.
The GTi-R DET has stronger main cap bolts.
The GTi-R DET has beefier rods.

-------------------------------------

However, if you have an SR20DE with low milleage and in good condition, there is nothing wrong with turboing it. Many have done it, without problems.

Thanks Spicez,

That helps a lot.

This is all kind of "in theory" anyway, because being student, he's got small budget, and is going all motor anyway.

Trying to get a 95 Pulsar with an SR20 to about mid 14 to low 15s quarter mile run. We figure with the standing kerb weight, we'd need about 140Kw at the flywheel.

I don't think it's possible on his budget, but it depends on how much he's willing to do himself.

Originally posted by spicez
Here are the differences between the DET and the DE:

The DET has a bigger oil pump.


Has anyone actually confirmed this? I strongly suspect that only the GTi-R has a bigger oil pump. The front cover of the DE is the same as the BB DET (at least outwardly).

Originally posted by spicez
The DET has a different front pulley.


This is definitely only the GTi-R.

Originally posted by spicez
The DET has lower compression pistons (8.3:1 vs 9.5:1).


The BB DET and the GTi-R DET have different compression ratios. I cannot remember which is which and really don't care because they are close anyway.

Originally posted by spicez
The DET has direct ignition.


Only the Silvia DET has ignition packs. The AWD DETs do not.

Originally posted by spicez
The DET has a variable intake cam, runs retarded at idle, advanced mid range and retarded top end.


Only the Silvia (RWD) DET.

Originally posted by spicez
The DET has mechanical shim in bucket type lifters with a slightly bigger in duration exhaust cam.


Only the GTi-R DET.

Originally posted by spicez
The GTi-R DET has individual Throttle body injection.

It is not throttle body injection. It does have individual throttle bodies however.

Originally posted by Sunder
Heck, I'm going to be running 7 pounds at 11:1 compression on my car soon.

Not for long you won't. :D

http://www.se-r.net/car_info/de_det_differences.html

Thats where I got the info, now that I think of it, your right, most of that I knew, I just copy pasted wihtout re-reading it.

Hmm, I guess Mike made a mistake a while back when he posted this.


BTW, Geo I never thanked you for those 944 links. Thanks.v

Originally posted by Geo91SER



The BB DET and the GTi-R DET have different compression ratios. I cannot remember which is which and really don't care because they are close anyway.



BB DET and Avenir DET 8.5:1
GTiR DET 8.3:1

Originally posted by eric96ser
BB DET and Avenir DET 8.5:1
GTiR DET 8.3:1

Geek. ;)

Originally posted by Geo91SER


Geek. ;)

Old Fart :cool:

Originally posted by Geo91SER

It is not throttle body injection. It does have individual throttle bodies however.

Now, if you know what throttle body injection is, you are probably both a geek -and- and old fart.

Originally posted by eric96ser


Old Fart :cool:

:eek: Ouch.

Originally posted by Driven97


Now, if you know what throttle body injection is, you are probably both a geek -and- and old fart.

Oh hell.... I even know what a carburator is. :p

Originally posted by Geo91SER


Oh hell.... I even know what a carburator is. :p

What about a DCOE???

Originally posted by Geo91SER


Not for long you won't. :D

I've known people to run the S2000 with 7 pounds of boost at 11:1 compression for over a year and 16,000 miles with no problems. This is on a stock engine.

It's all about tuning, keeping cylinder temperature down, tuning, high octane gas (pump gas is 98 here), tuning and did I mention, tuning?

Boostin 11.0:1 can and has been done. You just have to be more conservative on the tuning. Just look at the Matrix that SCC has turbo'd. And I think that might even be 11.5:1. But if you have lower compression, you can tune more aggressively for more power as you don't have to worry about detonation AS MUCH.

I need to take a S2000 for a spin sometime..... where do you have 98 octane?

Khiem

Originally posted by spdracerUT

I need to take a S2000 for a spin sometime..... where do you have 98 octane?

Khiem

Australia. Almost all service stations have 98 octane. Prices range from $1.60 a gallon to $2.00 a gallon. (Converted US pricing.) That's about $0.20 a gallon more than 92, standard octane fuel.

detonation have more determining factors than just boost and compression and timing. things like overall displacement, bore, cumbustion chamber shape, and torque all play a part in the likelyhood of detonation. i am not saying anyone is wrong here but things like 'i saw a honda do it' or 'the matrix in scc did it' is not an apples to apples comparison. an sr20de has trouble enough driving around on 11:1 compression.