How much boost can 9.5 Compression Ratio Pistons?
- Thread starter bango
- Start date
The 1UZFE EGR Delete Kit is available for sale here.
Second one is to aim for 800+ hp which will take a different path,and a shitload of folding stuff,as been demonstrated by a few threads..this one im all ears and advice..
So to cut to the chase,im leaning toward 9-9.5 CR for everyday drive atm..8.5 for the second motor..may only be a dream..lol
If you aim for 800 hp with a single turbo, turbo lag can't be avoided. I've driven a '91 modified single turbo Supra (I wasn't sure how many psi it had). I didn't know much about turbo back then. It always made me mad due to its lagging in heavy traffic. However, its power was crazy when the streets were clear and on the freeways. I never lost to any cars, including some exotic sport cars.
imported_steve_m
New Member
I,m running 9:1 on a bike engine and rotrex at 10 psi but wouldn't want to go higher
Joel (Jordy's Ski Boat) claimed to be running 12-14 psi boost with his marine setup, and that was using once-through river water in his water/air intercoolers. IIRC his charge air temps were down around 115 degrees F. I don't know what octane his fuel was. This was on a stock bottom end with the 10:1 compression.bango said:
imported_steve_m
New Member
Sorry, ought to have qualified that by saying with good intercooler and on UK 98 RON pump fuel. With race fuel I can run a bar of boost.
The compression ratio you run will vary between turbo and supercharger with further allowances for the size and type of supercharger.
If you run a turbo that comes on at (say) 3,500rpm you want the highest static ratio you can run to give the car some drivability down low.
If you run a big supercharger (Eaton M112) you can use the lower compression ratio as you will have boost from the moment you turn the key. Whilst a smaller supercharger (Eaton M90) needs ahigher static ratio for that all important bottom end.
With a centrifugal supercharger you need to go back toward turbo figures due to the "top end" nature of these superchargers.
If you run a turbo that comes on at (say) 3,500rpm you want the highest static ratio you can run to give the car some drivability down low.
If you run a big supercharger (Eaton M112) you can use the lower compression ratio as you will have boost from the moment you turn the key. Whilst a smaller supercharger (Eaton M90) needs ahigher static ratio for that all important bottom end.
With a centrifugal supercharger you need to go back toward turbo figures due to the "top end" nature of these superchargers.
Just iv been looking at the Clutch type Superchargers,my thoughts are if possible to have good fuel economy when driving normally,and "switch" of the SC when performance is required (heheh might be all the time..lol)So normal driving (static ratio)@9-9.5 CR,lower performance till "switched" on..Zuffen said:
stevechumo
Active Member
I've personally run around 10 psi turbo/intercooler on stock Honda engines with 10:5 compression (later stock Honda engines are average in strength). For more than 10 psi, I had to use forged dished 8:5 pistons, stronger rods & head studs...etc.
You haven't mentioned the fuel system & the ignition system that you'll use so watch out for them.
I've already bought a T04 turbo for my SC400 and I'll install it soon. My first stage would be everything in stock with around 7 psi with intercooler, FMU, Walbro hi-pressure hi-flow fuel pump, ignition box that can control the timing. And then, when it's up and running nicely, I'll increase the boost along with many things else.
You haven't mentioned the fuel system & the ignition system that you'll use so watch out for them.
I've already bought a T04 turbo for my SC400 and I'll install it soon. My first stage would be everything in stock with around 7 psi with intercooler, FMU, Walbro hi-pressure hi-flow fuel pump, ignition box that can control the timing. And then, when it's up and running nicely, I'll increase the boost along with many things else.
Well thats a good point,Iv no experience there thats why finding the limits to each application is what im after.The answer for me is to build 2 motors,one is for everyday driving with good economy and great performance (ok..ok i hear whats coming)around 500 fwhp,this with the help of the AMG E55 Supercharger..and a bit of NOS, i picked up,it has a electromagnetic clutch built in..should be good for everyday driving..on the present car (VL 1uz station wagon,family car..lol)My daughter loves it..
Second one is to aim for 800+ hp which will take a different path,and a shitload of folding stuff,as been demonstrated by a few threads..this one im all ears and advice..
So to cut to the chase,im leaning toward 9-9.5 CR for everyday drive atm..8.5 for the second motor..may only be a dream..lol
Yeah,im thinking turbos for the second motor too that T04 should get you some grunt for sure,Im just not sure about single turbos for V8's,though its better that nothing if space is a problem.Walbro fuelpump seem a good choice.What Hp are you looking for stevechumo ?As in now and near future for the SC400?
JustenGT8
New Member
A 9.5:1 static ratio will take 20psi no probs.....provided the rest of the setup is up to scratch. On the stock 10:1 pistons, with a good FMIC, 98RON fuel and WI my setup has seen 16psi with no detonation.
You are talking alot of variables though such as the efficiency of you FI system, quality of ECU, even cam timing will all determine your boost limit.
Don't get hung up on boost though as it's flow you are after...basically you want to run the lowest boost that will give you the flow to produce the hp you want eg a big turbo running 4psi gives the same flow as a smaller turbo running 10psi...both give you roughtly the same hp but the lower boosted engine is less stressed. Obviously, this is a bit simplistic as driveability etc factor in when developing a full package but demonstrates the point.
You are talking alot of variables though such as the efficiency of you FI system, quality of ECU, even cam timing will all determine your boost limit.
Don't get hung up on boost though as it's flow you are after...basically you want to run the lowest boost that will give you the flow to produce the hp you want eg a big turbo running 4psi gives the same flow as a smaller turbo running 10psi...both give you roughtly the same hp but the lower boosted engine is less stressed. Obviously, this is a bit simplistic as driveability etc factor in when developing a full package but demonstrates the point.
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stevechumo
Active Member
My first stage of hp is only from 350-400 crank hp, perhaps starting from 7-9 psi. I should have put it in rwhp but I don't like that low number. Also, I'd like to have a general idea when comparing with other car manufacturer's rated crank hp. I've heard that within 400 hp, the auto tranny will hold the power just fine. But more than that...umh...I'll be taking a big risk. Therefore, upgrading the auto tranny is a must (I know it can be done), or swapping in with a manual (I'm not sure if it can be done.)
If you aim for 800 hp with a single turbo, turbo lag can't be avoided. I've driven a '91 modified single turbo Supra (I wasn't sure how many psi it had). I didn't know much about turbo back then. It always made me mad due to its lagging in heavy traffic. However, its power was crazy when the streets were clear and on the freeways. I never lost to any cars, including some exotic sport cars.
Lextreme II
Active Member
In USA we get only 92 octan and I wonder how much boost would a 9.5 would support.
JustenGT8
New Member
Hard to say Lex as it depends on so many other factors but i just wouldn't bother trying to make big hp from 92 fuel....way too many compromises and you are going to be right on the tuning edge so a much higher chance of something going BANG.
If it were me i would have a nice safe 92RON tune which should still give some decent street grunt but for big hp i would be supplementing my octane is some way.....either a well respected octane booster, or race fuel mix. Use the good fuel and tune when you want some fun.....if you want fun all the time then that's the price you have to pay eh.
Horsepower...how fast to you want to pay
If it were me i would have a nice safe 92RON tune which should still give some decent street grunt but for big hp i would be supplementing my octane is some way.....either a well respected octane booster, or race fuel mix. Use the good fuel and tune when you want some fun.....if you want fun all the time then that's the price you have to pay eh.
Horsepower...how fast to you want to pay
92 octane is 98ron. Just an FYI for you auzzies. Our gas isn't "worse" than yours. It's the same thing for the most part.
9.5:1 pistons are pretty nice. While there are a ton of varriables to consider. The peak effective compression ratio compaired to a 10.5:1 piston is about 31psi VS 22psi. So there's another half bar of boost if the actual compression of 10.5:1 is stopping you from going higher.
Water/alcohol injection, as stated alot of times by me, is a huge safety barrier against detonation and lean tuning. $200-350 bucks for a really advanced system is great Throwing a good DIY $100-150usd kit together can't be beat if you're just looking for something to make it safer. (I mean what's one of those knock tuning things cost? $400-500 last I looked? I forget the name. The one that tunes each cylinder on the fly.)
Just an FYI for you auzzies. Our gas isn't "worse" than yours. It's the same thing for the most part.9.5:1 pistons are pretty nice. While there are a ton of varriables to consider. The peak effective compression ratio compaired to a 10.5:1 piston is about 31psi VS 22psi. So there's another half bar of boost if the actual compression of 10.5:1 is stopping you from going higher.
Water/alcohol injection, as stated alot of times by me, is a huge safety barrier against detonation and lean tuning. $200-350 bucks for a really advanced system is great Throwing a good DIY $100-150usd kit together can't be beat if you're just looking for something to make it safer. (I mean what's one of those knock tuning things cost? $400-500 last I looked? I forget the name. The one that tunes each cylinder on the fly.)
stevechumo
Active Member
I think 92 octane gas is still nice. There's only 91 octane down here in California.
