Turbo w/ High Compression

[92redman]

Nobody in the N/T board seemed to run forged 9:1 with their turbo setups, but I'm sure some people do over here. I'm planning to run Ross pistons and I am wondering what types of turbos respond the best to high compression with out getting too hot. How hard is it to tune and how much horsepower is reasonable with that type of set up.

I know that the Evo 8 has 8.8:1 compression with 19psi, so it can't be that terrible to tune can it?

Any help is appreciated.

By the way, I would rather not have anybody say, " Go with some stock turbo pistons" or something like that. I already have the pistons, thanks.

 

[GaRn]

you get a little better spoolup i believe, so a bigger turbo would always be nice! i dont think tuning is any harder, just have to have the bottom end to support it!

 

[92redman]

What else would have to be done to the bottom end, would the stock rods not be strong enough? I thought they could handle 400 to 450 hp.

 

[Mike 99GSX]

The higher compression pistons will not allow you to run quite as much boost as you may want to on pump gas and this is where your tuning threshold is a little less than with lower compression ones. You will spool the turbo faster though as the other guy said.

 

[kpt4321]

Higher compression makes the motor more efficient, so you can make the same power with less boost and fuel. However, you have to tune more carefully.


....Kyle T.

 

[GaRn]

Originally posted by kpt4321
Higher compression makes the motor more efficient, so you can make the same power with less boost and fuel. However, you have to tune more carefully.


....Kyle T.

 

[92redman]

So would it be better overall to use a larger turbo that would normally have more lag in order to take advantage of the compression? Would the 14b be too hard to get power to the ground in a FWD or would it be better to use that size turbo?

 

[GaRn]

hmmm, well it depends on what rods you have..

i tihnk this kind of equation works, maybe?

take the compression you want to have, say you want 9:1

and atmospheric pressure is around 14.7, so 14.7 * 9 = 132.3

stock compression is 7.8:1 and ppl have run up to like 25psi on stock bottom end or so from what ive heard.. so (14.7 * 7.8) + 25 = 139.66

that only leaves you like 8 psi to play with, hmmm now we know why them honda boys dont boost much!!

but if you have the fuel system to support it, the bottom end, and the headgasket, then you should be able to push much more than that.. of course this isnt taking into play CFM's of different turbochargers of course..

is what im doing somewhat correct? ..

 

[gritsak]

9:1 isnt "high compresion" even on a turbo motor...lots of honda guys are now switching from 9:1 to 10:1...theres more potential with the high compression with the right gas...the turbo will spool faster..the only downside is you can run as much timing and boost on pump gas and you will need more precise tuning, but you can also run a bigger turbo since it will spool a little quicker so the more airflow will make up for the less amount of boost you could run on pump compared to lower compression.

i think 9:1 is perfect for a street car...you can still run lots of boost on pump (15-20psi) and it will give you good low end..

 

[92redman]

How big of a turbo would be the most efficient? 20g or bigger maybe? What have others with 9:1 run? I am planning on running pump gas as well, don't have access to race gas within 20 mi. and as far as the rods go, I have a 6bolt motor.

 

[GaRn]

how fast do you want to go? i think you can get 400+ whp with the 20g..

 

[92redman]

I'm not necessarily looking to throw down certain hp numbers, just looking to run a turbo close to it's peak efficiency as possible while still being at reasonable boost levels for pump gas and mild to medium tuning, nothing that I couldn't do on my own.

I don't want to get too small of a turbo that I won't be able to hook up off the line and hit it's max boost before getting to the limits of my motor. On the other hand, I don't want such a large turbo that I'm not spooled up until 6k rpms, u know. I could easily look at what turbos people are running and decide which would fit my needs for 7.8:1, but I can't really find that same info for higher compression.

 

[GaRn]

hmm i would go with a 20g then.. you can get it internally wastegated..

thats the setup i have.. still have a little trouble with grip.. in 1st gear when boost comes youll prolly lose a little traction, even after youve gained traction from the launch.. you can get a 20g for like 700- 800 bucks or so i believe..

 

[92redman]

What would you guys recomend for tuning with that setup? Should I use the turbo ecu with the GM MAFT or would It be safer to tune with an S-AFC?

 

[GaRn]

it is possible to tune with the MAFT but it isnt as accurate as the SAFCII of course.. but id try with the MAFT first and if you can get decent results i wouldnt bother with the SAFC.. thats what i plan as well..

 

[92redman]

Nice...Maybe you can let me know how it turns out and give me a few pointers when you get your set-up working. I would rather have the S-AFCII, but I am a poor college kid that must buy my things one at a time, and that would be a pretty chunk of cash that I could put toward a frount mount or something.

 

[GaRn]

"poor college kid"

yea you and me both! might be till the end of winter till i get that, one of the last htings on my list unfortunately.. i have to get exhaust while the sale is on(RNR), pocketlogger, and fuel work..

 

[92redman]

Well, it will probably be next summer until I get everything together. I got some stock stuff I bought when I was gonna originally going to make a turbo kit for my stock n/t. Now that I have some forged internals on the way, I can go bigger and no longer desire to have the 14b.

Will the 20g bolt up to the 1g manny and o2 housing? Otherwise I'll try to sell that. I also have the stock smic and exhaust housing and wastegate actuator which I guess I will have no need for now. Oh well got everything for $40.

 

[GaRn]

Originally posted by 92redman
Well, it will probably be next summer until I get everything together. I got some stock stuff I bought when I was gonna originally going to make a turbo kit for my stock n/t. Now that I have some forged internals on the way, I can go bigger and no longer desire to have the 14b.

Will the 20g bolt up to the 1g manny and o2 housing? Otherwise I'll try to sell that. I also have the stock smic and exhaust housing and wastegate actuator which I guess I will have no need for now. Oh well got everything for $40.

yep sure will! might have to get different lower intercooler pipe setup since the turbo out is facing down..