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Old 02-07-2013, 01:13 PM   #201
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From what I understand if you are going for big turbo power and not running E85 you should go with 8.6:1 pistons. You will not be det limited and you can throw a **** ton of timing at it and make phenomenal power. I remember this discussion somewhere on this forum. I believe both Hustler and Savington said that 8.6:1 on pump gas will allow for the most head room.
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Old 02-07-2013, 01:16 PM   #202
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Originally Posted by Ryan_G View Post
I believe both Hustler and Savington said that 8.6:1 on pump gas will allow for the most head room.
This. I've never built an engine, but the TSE pistons page recommends 8.6:1 for their turbo builds. That's what I got, because Savington has probably built more turbo miata engines than just about everyone else on here. The MSM is 9.5:1 because it is an awful hack job that is more marketing than engineering.
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Old 02-07-2013, 01:17 PM   #203
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Originally Posted by Erat View Post
We get pretty good gas around here very high quality 94. Plus i have a few stations that sell e85. Not that i would need e85 for 9.5:1. Just because it's that "little bit more" in case i ever want to do silly things and make a ton more power than my current goals. Plus that CR will make my quick spool even quicker, and i like that. With that being said, i have not found any actual data showing how much of a difference 9:1 and 9.5:1 really is. I'd assume there would be some, if i were to even notice i doubt it. Maybe someone can prove me wrong.

The plan was to tear town the engine and get everything measured and figured out before ordering pistons. Like Vlad said i'll probably not bore it over unless i have to. 83.5mm seems to be what everyone is doing.

Edit* lower compression, crank the timing? I'm afarid to add timing, i'm tuned way conservative now.
Like Ryan G said, if you think you might want to go for big power later, you want to start with lower compression. 9:1 is a nice medium because you've got enough compression that it runs good off boost, but it's not too high of compression. If you go 9.5:1 you won't be able to run as much boost down the road. Yes you'll have more area under the curve, quicker spool like you said, but the headroom isn't there if you go higher compression and don't run E85.
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Old 02-07-2013, 01:45 PM   #204
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Dont be afraid of timing, timing is good. Timing is wholesome. Super conservative timing burns exhaust valves.
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Old 02-07-2013, 02:40 PM   #205
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Well. It sounds like a plan.
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Old 02-07-2013, 03:44 PM   #206
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Quote:
Originally Posted by turbofan View Post
Like Ryan G said, if you think you might want to go for big power later, you want to start with lower compression. 9:1 is a nice medium because you've got enough compression that it runs good off boost, but it's not too high of compression. If you go 9.5:1 you won't be able to run as much boost down the road. Yes you'll have more area under the curve, quicker spool like you said, but the headroom isn't there if you go higher compression and don't run E85.
Won't be able to run as much boost? Are you're talking more than 20psi? There are members here that have made 350whp on 9.5:1 w/ pump gas @ 20psi. I guess the Idea is you don't have to run as much boost if you have higher compression... The seesaw could go back and forth all day on this discussion though. It's preference. 8.5:1 all the way to 10:1 are all doable on pump gas. 10:1 having the smallest margin of error. 9.5:1 in my opinion is not a terrible option though.
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Old 02-07-2013, 05:01 PM   #207
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Originally Posted by krissetsfire View Post
Won't be able to run as much boost? Are you're talking more than 20psi? There are members here that have made 350whp on 9.5:1 w/ pump gas @ 20psi. I guess the Idea is you don't have to run as much boost if you have higher compression... The seesaw could go back and forth all day on this discussion though. It's preference. 8.5:1 all the way to 10:1 are all doable on pump gas. 10:1 having the smallest margin of error. 9.5:1 in my opinion is not a terrible option though.
I'm not putting a solid number on boost. If you want to run high boost, you will run it higher and safer with low compression. 9:1 is a great combination for this, as illustrated by the many cars that are well-built this way. There are members here who are putting out over 300 whp on a 1.6 with a 2560, but it's not the easiest/safest/best way to go. Yes you can make mad powers on 9.5:1 but Erat likes to play it safe, and if you're gonna put out lots of power safely, you're better off to go lower compression.

Last edited by turbofan; 02-07-2013 at 05:02 PM. Reason: first sentence was retarded
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Old 02-07-2013, 07:25 PM   #208
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Yeah, i want to be able to drive this car cross country, beat the **** out of it, then drive back.

Sustaining 35mpg highway would also be nice.
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Old 02-08-2013, 11:38 AM   #209
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The higher the static compression, generally, the better the BSFC.

In that case, if your goal is higher cruising mpg's then go for the 10:1 CR...
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Old 02-08-2013, 11:45 AM   #210
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Originally Posted by Efini~FC3S View Post
The higher the static compression, generally, the better the BSFC.

In that case, if your goal is higher cruising mpg's then go for the 10:1 CR...
This is also true. Lower comp will mean lower MPG. It can still be quite good, but I can't see 35 mpg. 30 though, sure.
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Old 02-08-2013, 11:57 AM   #211
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lol@ talking about MPG when building a high horsepower turbo engine.

What snail are you thinking about running Erat? Waiting on the TSE kit like me?
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Old 02-08-2013, 12:00 PM   #212
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lol@ talking about MPG when building a high horsepower turbo engine.

What snail are you thinking about running Erat? Waiting on the TSE kit like me?
Why lol at MPG when building a high horsepower turbo engine? If you do it right, there's no reason you can't have decent MPG when you're not on it, and amazing power when you are. Yeah if you're talking about 500hp then sure, that's pushing it.

Dillon, did you ever ride in Bryan's car? Is yours the fastest Miata you've ridden in? you might have to take mine for a spin when the weather clears up (if I still have it). 300hp would be fun but I don't really feel like I need any more than I have right now. 400 hp just seems silly!
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Old 02-08-2013, 03:29 PM   #213
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lol@ talking about MPG when building a high horsepower turbo engine.


Yes, you can have your cake and eat it too...
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Old 02-08-2013, 04:17 PM   #214
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This is also true. Lower comp will mean lower MPG. It can still be quite good, but I can't see 35 mpg. 30 though, sure.
I netted 35mpg with me, a passenger, and a full trunk of stuff returning from the dragon. Oh, and i had a good crosswind. I drove like an old man 65mph, and ever got into boost. But still. What's "high HP". To me high is like 500hp. But a normal 300hp (what i seem to be pretty reasonable) should still get great gas mileage just fine. I did all that ^ on 200hp. Nothing in my setup will change except engine internals. I don't see how my MPG would be affected except positively with the upped CR.

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Originally Posted by thenuge26 View Post
lol@ talking about MPG when building a high horsepower turbo engine.

What snail are you thinking about running Erat? Waiting on the TSE kit like me?
Going to keep the gt2560, with FM log manifold i currently have on it. I bought a bigger intercooler from Bryan, just waiting to hear back from him.

Quote:
Originally Posted by turbofan View Post
Why lol at MPG when building a high horsepower turbo engine? If you do it right, there's no reason you can't have decent MPG when you're not on it, and amazing power when you are. Yeah if you're talking about 500hp then sure, that's pushing it.

Dillon, did you ever ride in Bryan's car? Is yours the fastest Miata you've ridden in? you might have to take mine for a spin when the weather clears up (if I still have it). 300hp would be fun but I don't really feel like I need any more than I have right now. 400 hp just seems silly!
I'm not going to build around MPG, that's silly. But i wouldn't be mad if i could retain my 35mpg highway. Like i said, i want to be able to drive this thing somewhere. Nor am i shooting for 500hp.

My car is not the fastest miata i've been in. I was in a built engine, gt2860, begi S4 car on 30psi. BUT like all begi manifolds he blew a crack in it (on what i believe he said was his 4th manifold). Though, when i rode in it, we were on the dragon, so all the power was not usable. But it did feel good. Still haven't been in Bryan's, not sure i want to ruin his seats.

My main dilemma will be: Do i want to try and make the 5 speed last, or just shoot for the stars, blow it up, and find a 6 speed... Hmmm. Also my clutch is rated for 318ft/lb... We'll see.
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Old 02-08-2013, 04:32 PM   #215
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Well damn... that sounds like a tall order buddy.

My car has never seen higher than 25mpg, even on a whole highway tank.


And a fun and highly useless comparison, my MX6 makes more power, has a MUCH lower compression ratio (7.8:1), weighs more, and is shaped like a brick. 41mpg on the highway.
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Old 02-08-2013, 04:37 PM   #216
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If you run ALLOFIT out of that GT2560 your clutch will definitely be fine (still overkill actually) and unless you beat it your 5-speed should survive. But running ALLOFIT at 9.5:1 will not be easy to tune.
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Old 02-08-2013, 05:21 PM   #217
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Quote:
Originally Posted by concealer404 View Post
Well damn... that sounds like a tall order buddy.

My car has never seen higher than 25mpg, even on a whole highway tank.


And a fun and highly useless comparison, my MX6 makes more power, has a MUCH lower compression ratio (7.8:1), weighs more, and is shaped like a brick. 41mpg on the highway.
Why don't we all drive these ugly things? Sounds like magic.
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Old 02-08-2013, 05:39 PM   #218
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Originally Posted by concealer404 View Post
Well damn... that sounds like a tall order buddy.

My car has never seen higher than 25mpg, even on a whole highway tank.


And a fun and highly useless comparison, my MX6 makes more power, has a MUCH lower compression ratio (7.8:1), weighs more, and is shaped like a brick. 41mpg on the highway.
Sounds like your MX6 has a better tune than your miata...
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Old 02-11-2013, 10:42 AM   #219
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Originally Posted by Efini~FC3S View Post
Sounds like your MX6 has a better tune than your miata...
My MX6 runs horrible piggybacks that if i were to go into full detail of, would bring down the wrath of the MT.net gods upon my brow.

My MSM was tuned in-house by FM, the gods of turbo Miatas.

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Old 02-11-2013, 02:45 PM   #220
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I thought your MX6 had like three HKS F-con units, or something like that.

I don't think FM are gods of turbo Miatas...

Last edited by Efini~FC3S; 02-11-2013 at 02:46 PM. Reason: Grammar cat was po'd
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