2.1, 2.3, 2.4? + Gt35r

[93EclipseGSX]

alright time for the rebuild!!

ive been looking around doing my far share of reading, now im curious what you guys think, or what you would do in my situation.

overall power goals 450-500hp ( 92 octane )

Turbo : GT35R

Bottom End : 2.0, 2.1, 2.3, 2.4 ( you tell me which you pick )
* also all the kits ive been reading are really low CR i was thinking about
going with a higher CR like 9:1 or something to even make spool faster!
* not sure if im going to go with the more liter's and rev less or stay lower
and rev higher... i want this motor to last!

Transmission : Fully built TRE ( ready to shift past 8k if i choose to rev that high )

Tuning : Right just an sAFC, but willing to go AEM, or Power FC, or ?

goal of this car is weekend street killer with fastest spool!!

let me know what you guys think, and where should i get the work done? im into evo's so i know AMS makes really good parts, also buschur, what do you guys reccomend?

Thanks!

[Injected]

Originally Posted by 93EclipseGSX

alright time for the rebuild!!

ive been looking around doing my far share of reading, now im curious what you guys think, or what you would do in my situation.

overall power goals 450-500hp ( 92 octane )

Turbo : GT35R

Bottom End : 2.0, 2.1, 2.3, 2.4 ( you tell me which you pick )
* also all the kits ive been reading are really low CR i was thinking about
going with a higher CR like 9:1 or something to even make spool faster!
* not sure if im going to go with the more liter's and rev less or stay lower
and rev higher... i want this motor to last!

Transmission : Fully built TRE ( ready to shift past 8k if i choose to rev that high )

Tuning : Right just an sAFC, but willing to go AEM, or Power FC, or ?

goal of this car is weekend street killer with fastest spool!!

let me know what you guys think, and where should i get the work done? im into evo's so i know AMS makes really good parts, also buschur, what do you guys reccomend?

Thanks!

Believe it or not, higher CR doesn't spool the turbo faster, but will help with off boost performance. You will want the 2.4 for fastest spool obviously. DSMLink can handle it, SAFC cannot. Do the work yourself and learn while you do it. Pick a machine shop you can trust. Good luck. If you have any questions, throw them out there.

[talontsiturbo20]

I would go with a 2.4L set up with that turbo in mind. My 2.4 is the greatest motor ever for a street brawling car and does very well at the track. If you are looking for a streetable car that will blow the competition away, go with a 2.4 and use DSMlink. If you are looking for a race-motor, stay 2.0, and go with AEM.

Any questions about the build? Let me know.

J.P.

[suicidal2af]

Originally Posted by Injected

Believe it or not, higher CR doesn't spool the turbo faster, but will help with off boost performance. You will want the 2.4 for fastest spool obviously. DSMLink can handle it, SAFC cannot. Do the work yourself and learn while you do it. Pick a machine shop you can trust. Good luck. If you have any questions, throw them out there.

Higher CR will create faster spool. Higher CR creates higher EGTs(compress a gas more, it heats up more). Ideal gas law comes into play here -- PV=nRT. In our case, number of moles is a constant, as is volume. Raise temperature, raise pressure, create bigger pressure differential across the turbine, and voila, faster spool.

Going from 8.5:1 to 9:1 won't make a big difference, but one will be there nonetheless.

[GVR4592]

Originally Posted by suicidal2af

Higher CR will create faster spool. Higher CR creates higher EGTs(compress a gas more, it heats up more). Ideal gas law comes into play here -- PV=nRT. In our case, number of moles is a constant, as is volume. Raise temperature, raise pressure, create bigger pressure differential across the turbine, and voila, faster spool.

Going from 8.5:1 to 9:1 won't make a big difference, but one will be there nonetheless.

That is a very common misconception, a higher compression ratio will not create faster spool. It actually does the opposite. It lowers EGT's because of the higher expansion ratio, a higher expansion ratio give cooler exhaust gas, thus a slower spool. A higher compression engine will have more torque off boost and it may "feel" like the turbo is building boost sooner but it's not. The difference in spool time between 8:1 and 9:1 CR probably wouldn't even be noticeable, even with a fast datalogger.

[suicidal2af]

Originally Posted by GVR4592

That is a very common misconception, a higher compression ratio will not create faster spool. It actually does the opposite. It lowers EGT's because of the higher expansion ratio, a higher expansion ratio give cooler exhaust gas, thus a slower spool. A higher compression engine will have more torque off boost and it may "feel" like the turbo is building boost sooner but it's not. The difference in spool time between 8:1 and 9:1 CR probably wouldn't even be noticeable, even with a fast datalogger.

A higher expansion ratio will give you more cooling, but you EGTs will still be higher than from that of a lower CR. If you start out at, say, 850* C with an 8.5:1, and the expanding gas cools to 750*, we're 12% cooler. If our EGT starts at 950* C with 9:1, and cools to 800*C, we're 16% cooler, but still hotter than in the lower CR. What you said essentially mirrored what I said, in slightly different terms. The reason for the higher expansion ratio is that the pressure pre-turbine will increase -- after all, the volume of our combustion chamber and manifold is a constant. Increasing the pressure differential pre-turbine and post-turbine will -- you guessed it -- create a higher expansion ratio.

Compressing the air in the combustion chamber further will increase temperature. Unarguable fact. Raising the temperature, if we follow the ideal gas law, will increase pressure. The only way for that pressure to release is through our exhaust. Thus, increased velocity, and a higher expansion ratio.

That said, the different of 8:1 and 9:1 would be *maybe* 100-200rpms. However, going from 7:1 to 9.5:1 would yield a very noticeable difference.

[GVR4592]

Originally Posted by suicidal2af

A higher expansion ratio will give you more cooling, but you EGTs will still be higher than from that of a lower CR. If you start out at, say, 850* C with an 8.5:1, and the expanding gas cools to 750*, we're 12% cooler. If our EGT starts at 950* C with 9:1, and cools to 800*C, we're 16% cooler, but still hotter than in the lower CR. What you said essentially mirrored what I said, in slightly different terms. The reason for the higher expansion ratio is that the pressure pre-turbine will increase -- after all, the volume of our combustion chamber and manifold is a constant. Increasing the pressure differential pre-turbine and post-turbine will -- you guessed it -- create a higher expansion ratio.

Compressing the air in the combustion chamber further will increase temperature. Unarguable fact. Raising the temperature, if we follow the ideal gas law, will increase pressure. The only way for that pressure to release is through our exhaust. Thus, increased velocity, and a higher expansion ratio.

That said, the different of 8:1 and 9:1 would be *maybe* 100-200rpms. However, going from 7:1 to 9.5:1 would yield a very noticeable difference.

I have done testing on this with my AEM and there is 0 loggable difference between 7.6:1 and 8.8:1. The turbo spooled within 25 rpms with the different compression ratio's. All I did was change pistons and that was it. Ring gap was the same, piston to cylinder wall clearance was the same, headgasket, etc,etc. I made A/F exactly the same with both pistons, then I optmized A/F for the 8.8, there was still no change.

I don't monitor egt's so I don't know what the difference would be in exhaust temps. How would you determine( without monitoring egt's) how much of a temperature change there would be from changing compression? Or how much more it will cool during the expansion stroke? Does the ideal gas law calculate that?

[fourreGsixty3]

Glad I found this thread because its almost exactly what Im going to be going with. I am going with a 2.3L, GT35r. Ive heard this combo has great results.

[andymoraitis]

I can confirm a difference in EGT readings between a 16G on an 8.5:1 2.0 and an 8.8:1 2.3 stroker at the same boost levels, same tune and same timing advance. EGT's were 150 degrees cooler at peak on the higher compression 2.3 than with the lower compression 2.0. Interestingly enough, the only benefit to the increased displacement was greater off boost power, but spool between the two motors was nearly identical on Comp 200's (~3700 RPM) and the same boost levels (24 psi).

[nightspeed87]

but you probably gained a massive amount of torque with the 2.3 opposed to the 2.0 am i correct? Your making it sound like the only thing the stroker did for you was give you more off boost power, id think bigger engine/ more a/f, therefore more power requardless....Did you ever dyno your car before and after the stroker set up at the same psi, im curious of power band differences, and hp figures, im sure the power hits a lot harder and sooner in the stroked engine...

[fourreGsixty3]

The 2.4L will help spool the GT35R faster then the rest, because of the displacement. the strokers aren't as high reving engines as the 2.0s because they are more torquey. the 2.3L with the GT will get you to your mark easily. With the 2.3L you can use rods that are 5.900"s long, same as 1G rods. The amount that the different CR ratio's will change off boost power is negligable. I would choose an 8.5:1 ratio, thats what Darren over at FFWD uses on all of there engines, and some of those are pushing 600+hp. With a set of stroker cams like the FP 3s the 2.3L will spool the GT fully around 4k rpm. with the 2.4Ls it has been found that some people have had to knock the oil pan out a little due to the rod bolts tapping it. This of course only some people, not all, and its been debated what the cause is, but it hasnt been documented that this problem occurs with 2.3Ls so I would just get the 2.3L. If your looking to go 9+k shifts, with drag in mind you may want to stick with the 2.0, and build that up with the GT, like I said before the 2.0 is a more rev happy engine then the strokers, and Shep still uses a 2.0 due to this fact, but if 7k is the max you will go with more 5k shifts then this is a great engine. Ill be getting mine from Darren at FFWD in the near future with a GT35R turbo to power it. The lower compression the more boost you can run on pump gas, 8.5 will be good for anything seen on the street, or weekend warrior cars.

Dustin

[andymoraitis]

Originally Posted by fourreGsixty3

the strokers aren't as high reving engines as the 2.0s because they are more torquey

Actually, it's because of the piston/rod angle. Rev them too high on a repeated basis and you'll wear the cylinder into an oval shape.

Nightspeed: My car has never seen a dyno, however there was a distinct difference between the 2.0 and 2.3 in terms of torque. I saw NO difference in spool characteristics however. Even with very lean A/F's at the onset of boost to generate heat, my 50 trim doesn't hit 25 psi until 4400. Both my 2.0 and 2.3 have been late spoolers, but I'm not going to complain since the top end power is insane. For reference, I shift at 7000.

[talontsiturbo20]

Originally Posted by fourreGsixty3

The 2.4L will help spool the GT35R faster then the rest, because of the displacement. the strokers aren't as high reving engines as the 2.0s because they are more torquey. the 2.3L with the GT will get you to your mark easily. With the 2.3L you can use rods that are 5.900"s long, same as 1G rods.

Dustin

The 2.4L also uses 5.9" rods. The only disadvantage with the 2.4 is the clearance issues with all of the timing belt covers, and the fact that no body makes a kevlar timing belt for a 2.4L. The advantage is that you don't have to machine your block for crankshaft clearance.

J.P.

[4wd-Eclipse]

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[fourreGsixty3]

Originally Posted by talontsiturbo20

The 2.4L also uses 5.9" rods. The only disadvantage with the 2.4 is the clearance issues with all of the timing belt covers, and the fact that no body makes a kevlar timing belt for a 2.4L. The advantage is that you don't have to machine your block for crankshaft clearance.

J.P.

If the 2.4 uses 5.900" rods like the 2.3, then what is the difference? The pistons? I would have thought that the rods would be longer, and pistons shorter to keep them from popping out the top of the block. I know that there are different pistons for 2.4s to 2.3s, but would this change it .1Ls?

dustin

[fourreGsixty3]

Originally Posted by andymoraitis

Actually, it's because of the piston/rod angle. Rev them too high on a repeated basis and you'll wear the cylinder into an oval shape.

Nightspeed: My car has never seen a dyno, however there was a distinct difference between the 2.0 and 2.3 in terms of torque. I saw NO difference in spool characteristics however. Even with very lean A/F's at the onset of boost to generate heat, my 50 trim doesn't hit 25 psi until 4400. Both my 2.0 and 2.3 have been late spoolers, but I'm not going to complain since the top end power is insane. For reference, I shift at 7000.

Andy maybe changing out your 200s for a set of stroker cams would help some Also what do you think would be too high of a shifting point on repeated occasions? 7K? 8K?9K?
Just would like a little reference. Because you say you shift at 7K, is this too high, or are you just saying that they shift up there nicelt at redline repeatedly with no oval shaped wear on the cylinder wall?

Dustin

[andymoraitis]

When I had everything machined, I spoke to SBR and asked them what a safe shift point for the motor was. They recommended 7K. I've spun this thing to 8000 to check rev limiter function, but I'd never shift higher than what I do now for racing purposes. Your best bet is to ask your engine builder what he recommends. Keep in mind that I'm also on a stock valvetrain and I don't need to go any further than I have to.

As far as cams go, I'd rather get a set of adjustable gears and advance the intake cam a few degrees. It's not like I'm revving so high that I'll miss the top end.

[Lurker]

Originally Posted by fourreGsixty3

If the 2.4 uses 5.900" rods like the 2.3, then what is the difference? The pistons? I would have thought that the rods would be longer, and pistons shorter to keep them from popping out the top of the block. I know that there are different pistons for 2.4s to 2.3s, but would this change it .1Ls?

dustin

The difference between 2.4s and 2.3s is not really the .1L difference.

2.4 is when you use a 2.4L block (e.g. 4g64) with a stroker (4g64) crank.
2.3 is when you use a 2.0L block (e.g. 4g63) with a stroker (4g64) crank.

Rod length is usually the same, but with 2.4L you have the option to use a longer rod ( because of the higher deck height ) to allow for a more favorable rod angle.

Note: longer rod does not give you higher displacement.

[fourreGsixty3]

Oh ok, yeah I was looking at a 2.4L stroker kit from BC and his has a 102mm 7 bolt crank, and the 2.3s have a 100mm crank, is this also part of the difference? Or just the higher deck of the 2.4L block with 2.4l pistons?

Dustin