Low comp vs High comp

Turbo and Supercharger discussion
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Low comp vs High comp

By Ecc0
- Sun Jul 01, 2012 5:13 am #309833 So for some time now (to long) I've been saving and buying up parts to go boost in my B series coupe. My plan had always been to low comp and get a nice reliable 280hp for DD.

Recently I've seen more and more people build High comp turbo setups and know this gives you more torque which as we all know is where Honda engines are lacking most.

What are your views opinions on both, pro's and con's???

As said I wanted around 280hp but if that dropped down to 250hp but my torque was better with High comp boost that wouldn't be a problem for me.
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By poorman type-r
- Sun Jul 01, 2012 7:01 am #309841 When you say high comp. How high are you talking? 12:1?

If you are looking for instant boost and torque, you should supercharge instead of turbo. IMO.
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By Ecc0
- Sun Jul 01, 2012 9:17 am #309850 Yes would be looking at a cr of 12.1-1 already have my turbo kit and most other bits just looking to build up my spare bloke before I fit everything
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By teal_dx
- Sun Jul 01, 2012 2:36 pm #309857 If you can find a confident tuner then guide it a try. I wouldn't try it on my Daily driver though. A boosted car is already less reliable. A high compression boosted car has even more room for error. What turbo kit do you already have? If you bought a turbo with low compression build in mind, then it is probably going to be overkill for a high compression motor.
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By suspendedHatch
- Tue Jul 03, 2012 4:53 am #310018 Are you going to be running E85? Race gas?

12:1 on its own requires high octane. It also reduces the chamber volume. With a turbo, you're better off with "normal" compression ie around 10:1. That's what people mean when they say high compression for a turbo. They're speaking relative to the normal 8:1 that people downgrade to for turbo setups. That is unless I've missed some miraculous development in the last year or two.

Relatively high compression with a smaller turbo is more desirable than low compression higher boost IMO. You need good engine management and a good tuner. You're going to need to put some thought into the build. I would find someone that has put a couple together.

By EJ1_MK
- Tue Jul 03, 2012 7:54 am #310026 You will want to find some one to tune like TEAL_DX said, as far as volume is concerned most race drag cars run high compression and like 30 + lbs of boost. If your lower end is built and you have head studs then you should be fine. you will most likely make more power at lower boost than the guy that runs 20 lbs on a 10:1 comp motor.

Local speed shop on a gsr block with 13.5:1 comp pushes 32+ and makes close to 1000hp drag car.

I would talk to your local shops and tuners and see what they can tune for and what they have tuned for. Also like teal_dx said I would either keep the boost low if your going to daily it at all.

By bigpunn421
- Tue Jul 03, 2012 11:29 am #310029 for your power goals you could get away with a stock b series motor. save that money and put it into a tune, turbo, fuel setup or exhaust.


look into water/meth or e85+ if you want a high compression turbo motor daily driver.

if you have the same bolt ons and everything was the same except the compression, the higher compression motor will always make more power and torque over the lower compression. there is a give/break point. you dont want it to high or too low.

usually you have to consider fuels and ask your tuner what he feels would be best like mentioned above. higher the octane the higher you can safely bump compression.
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By Ecc0
- Wed Jul 04, 2012 5:27 am #310093 Wow thanks for everyone's input. I'm in the uk so will be running 99octane so if I go the High comp route I'll be fine, as this is a new way of thinking for me I didn't realise 10:1 cr was classed as High comp on a turbo engine so thanks for letting me know, that also means I could run standard internals on my B16a2 to achieve my power goals.

I have been doing serious shopping about for nearly 2 years now to find the right tuner as my good friend and tuner passed away and have struggled to find anyone else I will trust with my car let alone anyone that comes out with reliable information.

No matter what I'm looking to rebuild the engine so be at least doing new piston rings though am still leaning towards a Low comp build 9:1 or maybe 8:1.

By bigpunn421
- Wed Jul 04, 2012 9:46 pm #310133
Ecc0 wrote:Wow thanks for everyone's input. I'm in the uk so will be running 99octane so if I go the High comp route I'll be fine, as this is a new way of thinking for me I didn't realise 10:1 cr was classed as High comp on a turbo engine so thanks for letting me know, that also means I could run standard internals on my B16a2 to achieve my power goals.

I have been doing serious shopping about for nearly 2 years now to find the right tuner as my good friend and tuner passed away and have struggled to find anyone else I will trust with my car let alone anyone that comes out with reliable information.

No matter what I'm looking to rebuild the engine so be at least doing new piston rings though am still leaning towards a Low comp build 9:1 or maybe 8:1.


10to1 isnt high for turbo. but i guess everyones high and low is different. i have 10.6to1 with 11psi daily driven on 93octane. i have a buddy down the road with a jdm itr turbo and he makes over 350whp stock motor. jdm itr is 11to1. i would rather have a 1.6 daily boosted than a 1.8

also smaller displacement the safer you will be. smaller displacement can take more psi than a bigger one. so a stock motor 1.6 is safer than a 1.8 if compression is the same


also you have to remember the lower the compression the less efficient the motor becomes.

the higher the compression = more energy... energy=power

but too much boost and too much compression could cause detonation. theres a give/breaking point. so you want to research.


compression, size of turbo, IAT, altitude, weather conditions, what octane gas and how well the car has been tuned has to be considered. not just the compression of the motor. so if you give me more details i can help you a bit more.
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