fyi, wiseco does not make a 9.0:1 piston - Page 4 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-16-2007, 03:38 PM   #61
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1.) What is value upgrading from the stock pistons with only 250whp. I know the rings don't like that much but can't you just install better rings? Stock pistons and some descent RODs and this could be a done deal. Am I missing something?

2.)What with the big(er) turbo why didn't you use the GT2560R to hit your goal?


3.)Reading this thread I have to ask why didn't you go with a supercharger instead of a turbo to avoid lag?
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Old 11-16-2007, 03:38 PM   #62
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Quote:
Originally Posted by hustler View Post
does anyone actually have experience with a low compression motor?
Yes.
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Old 11-16-2007, 03:40 PM   #63
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Originally Posted by PAT! View Post
So with a .4 bump in compression it would have gone from 135lb/ft to 465 in 690rpm. How has the situation been improved?
because more exhaust energy would hopefully get the turbo spooling sooner. Are we sure that the 4% rule is a linear relationship to RPM? I seriously doubt it is.

The corrado made lots more power naturally aspirated in the lower rpm range than it did with the turbo and low compression motor.
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Old 11-16-2007, 03:42 PM   #64
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Quote:
Originally Posted by kingofl337 View Post
1.) What is value upgrading from the stock pistons with only 250whp. I know the rings don't like that much but can't you just install better rings? Stock pistons and some descent RODs and this could be a done deal. Am I missing something?

2.)What with the big(er) turbo why didn't you use the GT2560R to hit your goal?


3.)Reading this thread I have to ask why didn't you go with a supercharger instead of a turbo to avoid lag?
1.) peace of mind when I'm at the track 4 hours from home
2.) Corky recommended it since its a track car
3.) because no one would sell me a mp62 with no electronics, and they typically don't make as much power as I want until they spin a high enough RPM to have reliability in question
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Old 11-16-2007, 03:47 PM   #65
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Originally Posted by hustler View Post
because more exhaust energy would hopefully get the turbo spooling sooner. Are we sure that the 4% rule is a linear relationship to RPM? I seriously doubt it is.

The corrado made lots more power naturally aspirated in the lower rpm range than it did with the turbo and low compression motor.
My point being that spooling sooner is not going to radically alter that powerband in the example you gave. Not without changing the turbo. You are giving an example so extreme it has little bearing on your current setup. For what it is worth that car was not in anyways well sorted. 2.9 liters making that sort of power there is not reason for a powerband that peaky. There was one or more serious flaws either in the design or the execution.

Drive a 1st gen DSM, 7.8 compression. No lag.
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Old 11-16-2007, 03:50 PM   #66
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See Foundsoul's recent dyno chart. His powerband is huge, with only 1600 cc's of fury to spool his 2560. You'll have 1900 cc's on a 2860. Should be comparable in terms of spool, but you'll have more power everywhere. You'll have a better head too.
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Old 11-16-2007, 03:59 PM   #67
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PAT! - I'm kinda gonna call BS on the eclipse I've had both 6 and 7 bolt GSX eclipses 14b and t25 and they were both kind of dogs down low. Don't get me wrong they could get going and porting, upgrading piping, manifold and downpipe helped. But it still took a bit to get going from below 2500rpm. Once the motor was around 3500rpm a jab of the throttle would create a possessed monster I'm sure you know all about that. I miss those cars....

Miata is better though
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Old 11-16-2007, 04:07 PM   #68
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even the newer evo's suck ***** out of boost, and they're at 9.0. I'd like to know if anoyne has ever tuned an 8.6:1 motor to not drive like ****. I'm confident in my road tuning ability to make it work, if its possible.
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Old 11-16-2007, 04:21 PM   #69
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Quote:
Originally Posted by kingofl337 View Post
PAT! - I'm kinda gonna call BS on the eclipse I've had both 6 and 7 bolt GSX eclipses 14b and t25 and they were both kind of dogs down low. Don't get me wrong they could get going and porting, upgrading piping, manifold and downpipe helped. But it still took a bit to get going from below 2500rpm. Once the motor was around 3500rpm a jab of the throttle would create a possessed monster I'm sure you know all about that. I miss those cars....

Miata is better though
Yeah, maybe "no lag" wasn't the right way to put it... but as a counterpoint to a powerband tripling in the span of 700rpm due to having 8.5:1 compression I figured it was the best (likely to be in the realm of experience of anyone here) example.

And for what it is worth, tuning eliminates that sluggishness...

Also, MKIV Supras have 8.5 stock... as do GENIII 3sgtes (MR2, Celicas). Neither of which are slouches.
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Old 11-16-2007, 04:23 PM   #70
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Quote:
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I'm confident in my road tuning ability to make it work, if its possible.
Wasn't it earlier this month that said you didn't trust yourself to do any road tuning, for fear of messing something up? Not choosing correct AFR? Geez man...
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Old 11-16-2007, 04:25 PM   #71
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I had a 88 300ZX Turbo. It was 100% stock. 8.3:1 compression and it spooled at 3500. With some aftermarket parts and a new ecu, it would probably spool closer to 2500. It made decent power before it spooled. I wouldn't say it drove like ****. The turbo could have spooled sooner.


How a car drives is not controlled by compression alone. 0.4 points of increased compression will not make a ****.
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Old 11-16-2007, 04:26 PM   #72
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Wasn't it earlier this month that said you didn't trust yourself to do any road tuning, for fear of messing something up? Not choosing correct AFR? Geez man...
Playing with ms for a few hours last weekend inspired confidence.
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Old 11-16-2007, 04:29 PM   #73
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Define "drive like ****". If after tuning the proposed 8.5 motor with a standalone you can't get to within 5% of a completely stock car you don't need to be tuning it yourself. And if you expect your off boost power with your turbo set-up to exceed the power it made NA than you have unrealistic expectations.

And it itsn't all about peak numbers, but throttle and transient response will all come down to the tune.
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Old 11-16-2007, 04:35 PM   #74
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My turbo spooled to 12psi @ 4.4K

it now spools to the same at 3.4K. I shaved 1000RPM off the spool with exhaust and mild headwork alone.

and it's a 1.6L and has a bigger turbine than your 2860RS IIRC.
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Old 11-16-2007, 04:37 PM   #75
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Originally Posted by Braineack View Post
My turbo spooled to 12psi @ 4.4K

it now spools to the same at 3.4K. I shaved 1000RPM off the spool with exhaust and mild headwork alone.

and it's a 1.6L and has a bigger turbine than your 2860RS IIRC.
9.0:1?
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Old 11-16-2007, 04:40 PM   #76
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who give's a funk?!
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Old 11-16-2007, 04:41 PM   #77
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Originally Posted by Braineack View Post
who give's a funk?!
I'd like to know if people are getting results like this with low comp motors.
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Old 11-16-2007, 04:45 PM   #78
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but the point here is I shaved that much off without changing my compression or spark map.
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Old 11-16-2007, 04:50 PM   #79
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but the point here is I shaved that much off without changing my compression or spark map.
what turbine wheel do you have?
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Old 11-16-2007, 04:55 PM   #80
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Hustler-read. http://www.musclemustangfastfords.co...tio/index.html

Using the 4% rule. Assuming you make 250whp with 9.0:1 ratio pistons.

9.0-8.6=0.4 This is the change in compression

.4 X 4%= .016 This is how much power will change.

1-.016= .984 This is your new power factor.

250whp X .984= 246whp with 8.6:1 compression. That's a 4WHP difference, which would be almost undetectable.
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