low compression with no boost
10-17-2006, 02:06 PM
#1
4th Gear Member
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Join Date: Feb 2004
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low compression with no boost
How much power would I lose if I used a forged short block with low compression (8:1) that was designed for f/i but ran it n/a? Reason I ask is I need a new motor and a forged short block is looking like the only viable option.
I really want to add a blower but dont have the money now. It would suck to have a block with 9+:1 compression built then want to f/i it later. Its one of those do it once, do it right things. So what would I lose if I had a low compression motor n/a and drove on that until I had the money to f/i it?
I really want to add a blower but dont have the money now. It would suck to have a block with 9+:1 compression built then want to f/i it later. Its one of those do it once, do it right things. So what would I lose if I had a low compression motor n/a and drove on that until I had the money to f/i it?
10-17-2006, 02:43 PM
#2
5th Gear Member
Join Date: Aug 2005
Location: Whitehall, Michigan
Posts: 2,638
RE: low compression with no boost
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
10-17-2006, 03:31 PM
#3
3rd Gear Member
Join Date: Aug 2006
Location: Upstate NY
Posts: 621
RE: low compression with no boost
ORIGINAL: ShadowDrake
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
10-17-2006, 03:46 PM
#4
6th Gear Member
Join Date: Jan 2004
Location: United States
Posts: 12,575
RE: low compression with no boost
ORIGINAL: ShadowDrake
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
If your going to rebuild the shortblock for boost, the only way to go is a lower compression engine. Lowering the compression WILL cost you power n/a, and with no other changes will acutally lower it FI. The difference is, you can run more timing and more boost on the same engine with a lower compression ratio, and thus make more power overall.
I would say, if you have to buy a shortblock now get the lower compression setup, and then just put up with making less power for now. I honestly cannot give you an accurate idea of what it will cost you, but it probably will be fairly significant.
The gains in the end will far outweigh the costs now though.
10-17-2006, 03:54 PM
#5
Underboss
Join Date: Jan 2006
Location: Helaware
Posts: 20,273
RE: low compression with no boost
ORIGINAL: ShadowDrake
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
10-17-2006, 03:59 PM
#7
6th Gear Member
Join Date: Jan 2004
Location: United States
Posts: 12,575
RE: low compression with no boost
ORIGINAL: lizzyfan
I did the PI swap and have 10.5:1 compression. I now have a Vortech S/C (see sig) and running about 8 psi on stock internals. Sure if I had the extra cash I would of went with the forged internals but not so in my case. I have a good tune on it and I'll be fine. I am not gonna beat the p*ss out of it!!!
ORIGINAL: ShadowDrake
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
No question if you want to run big boost numbers and street gas you need to run a lower compression setup .
10-17-2006, 04:06 PM
#8
Underboss
Join Date: Jan 2006
Location: Helaware
Posts: 20,273
RE: low compression with no boost
ORIGINAL: 2000GT4.6
Just make sure you get a great tune, and run high octane gas. From what I have seen, with the higher compression you have to run less timing even with 8 PSI, and will end up making less power than a PI swapped car.
No question if you want to run big boost numbers and street gas you need to run a lower compression setup .
ORIGINAL: lizzyfan
I did the PI swap and have 10.5:1 compression. I now have a Vortech S/C (see sig) and running about 8 psi on stock internals. Sure if I had the extra cash I would of went with the forged internals but not so in my case. I have a good tune on it and I'll be fine. I am not gonna beat the p*ss out of it!!!
ORIGINAL: ShadowDrake
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
You can still run boost with higher compression... whoever tells you that you can't is wrong. Compression = power, that's all there is to it.
I can't say exactly how much power you'll lose with the lower compression, you'll definitely notice it feeling weaker, especially down low... I want to say somewhere around 10% power for 2 points of compression but don't hold me to that at all. You'll be fine driving around N/A with a low compression block, though, you'll get better gas mileage and more power with a higher compression one.
No question if you want to run big boost numbers and street gas you need to run a lower compression setup .
10-17-2006, 04:31 PM
#9
4th Gear Member
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Join Date: Feb 2004
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RE: low compression with no boost
Ok...so If ive got this right, a stock compression ratio would be fine for a streetable f/i car (99+ pi) making about 400-450rwhp with forged internals and 93 pump gas? Im not looking for anything over 450rwhp out of this car...but I want to run it on pump gas. Any really serious hp numbers would require the lower compression and massive ammouts of boost which is not what Im after...correct?
10-17-2006, 07:23 PM
#10
Join Date: Oct 2006
Location:
Posts: 47
RE: low compression with no boost
Somebody throw me a bone here -- my toy, prior the stang was an 03 Evo VIII (may it rest in peace); I was running .2 more than stock, just around 9.0:1 compression ratio and running 24psi of boost (turbo). Now, I would think that anything less than 12psi would be completely safe with stock compression, 9psi or less for stock internals (else replace your head studs, head gaskets, et cetera). Higher than that, I would say you need to run a lower compression ratio.
You definately need to run 93 octane gas (or if you unluckly enough to live in that 91 octane state, well make due) if you are going to use forced induction, and get a decent tune to avoid detonation.
My opinion, with this and $3 you can get that beer at happy hour; your mileage may vary.
-- Dave