High compression, low boost?

[JOMARO]

I maxed a s256sx out on my stock s52 rods. It made 465whp/418wtq. As soon as I put the 366sxe in on e85 at 21psi it bent several rods after just a few quick pulls.

any idea what power did you have before bending those rods ?

[rajicase]

any idea what power did you have before bending those rods ?

Not sure honestly didn't get to dyno, whatever 21 psi from a s366sxe on E85 on an s52 is.

[Northern]

Stock CR + 91 + 6-8 psi is more than reasonable.

I'm running an S257+12psi on a stock M52b28(ie. No spacer, no ARPs) with no problems yet.

[Wes1311]

Stock CR + 91 + 6-18 psi is more than reasonable.

I'm running an S257+12psi on a stock M52b28(ie. No spacer, no ARPs) with no problems yet.

Do you have a build thread? I'm curious


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[BadBoostedBmwM3]

Stock CR + 91 + 6-18 psi is more than reasonable. I'm running an S257+12psi on a stock M52b28(ie. No spacer, no ARPs) with no problems yet.

Fuel?

[pbonsalb]

6-18 psi is ok on 91 with stock CR? Show me an S52 running 18 psi from a GT4094R on stock compression with 91 octane. I'd stick to 10 psi from a smaller turbo to be safe.

[rajicase]

6-18 psi is ok on 91 with stock CR? Show me an S52 running 18 psi from a GT4094R on stock compression with 91 octane. I'd stick to 10 psi from a smaller turbo to be safe.

I don't think 18 psi from a 30r would be safe on 91 and stock cr..

[e30polak]

Pretty sure he meant 6-8 psi, not 18, lol.

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Same price for the Garrett GTW 5857 , or the GTW 6262 is a hair more. But too much for a street 2.5L

Unless he stays stock CR with a cutring and studs and uses e85

[pbonsalb]

OK. That makes sense. Even 10-12 psi on the outside has been OK for many. But 18, no way.

To me it just is not worthwhile to not do the HG unless you are running E85 and your motor is in good shape and you have a smaller piston block for better head sealing. People get used to low boost fast and want more, and then they blow the gasket or break stuff.

[tyr283]

OK. That makes sense. Even 10-12 psi on the outside has been OK for many. But 18, no way.

To me it just is not worthwhile to not do the HG unless you are running E85 and your motor is in good shape and you have a smaller piston block for better head sealing. People get used to low boost fast and want more, and then they blow the gasket or break stuff.

Well for me this wasn't about not doing HG, it's getting a cutring either way. Just figured high compression would be nice for spool and off-boost manners for a street car on low boost and we all know E85 is fine for high boost kill mode

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[NOTORIOUS VR]

Well for me this wasn't about not doing HG, it's getting a cutring either way. Just figured high compression would be nice for spool and off-boost manners for a street car on low boost and we all know E85 is fine for high boost kill mode

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lowering compression doesn't really hurt response or spool if at all. You're able to make back almost all the loss in efficiency by running more ignition timing off boost.

[tyr283]

lowering compression doesn't really hurt response or spool if at all. You're able to make back almost all the loss in efficiency by running more ignition timing off boost.

I was just worried about more ignition timing with 91 octane on the DD tune. I'm probably going to shoot RK Tunes an email and see what they recommend

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[e30polak]

lowering compression doesn't really hurt response or spool if at all. You're able to make back almost all the loss in efficiency by running more ignition timing off boost.

True, but the other side of it is that stock compression and e85 with e85 will make more power on less boost. Spool and off boost response is better with higher compression, but being able to drive around town at 15 psi on 91 is worth it compared to only 6-8 psi. Now if you plan to run e85 more of the time, then I'd stay stock compression, as you will make the most power. Dean made more power at 18 psi than his buddy did at 20 psi, with a gt35r (vs. his friend's gtx35r), with better spool because he was stock compression on e85 and his friend was at 8.5:1.

[BadBoostedBmwM3]

True, but the other side of it is that stock compression and e85 with e85 will make more power on less boost. Spool and off boost response is better with higher compression, but being able to drive around town at 15 psi on 91 is worth it compared to only 6-8 psi. Now if you plan to run e85 more of the time, then I'd stay stock compression, as you will make the most power. Dean made more power at 14 psi than his buddy did at 18 psi, with a gt35r (vs. his friend's gtx35r), with better spool because he was stock compression on e85 and his friend was at 8.5:1.

Can you link the original post to that picture?

[NOTORIOUS VR]

True, but the other side of it is that stock compression and e85 with e85 will make more power on less boost. Spool and off boost response is better with higher compression, but being able to drive around town at 15 psi on 91 is worth it compared to only 6-8 psi. Now if you plan to run e85 more of the time, then I'd stay stock compression, as you will make the most power. Dean made more power at 18 psi than his buddy did at 20 psi, with a gt35r (vs. his friend's gtx35r), with better spool because he was stock compression on e85 and his friend was at 8.5:1.

You're comparing a GTX to a GT turbo... that's enough to make up the difference... I don't see how that is a valid comparison at all.

Stock compression on E85 might make slightly more if anything.. but it won't make a lot more vs lower CR on E85... again, it's really not a big of a difference that people think it is. Drop CR and add ignition timing, or leave CR and be knock limited and reduce ign timing (unless your fuel doesn't limit you). The differences really are minimal. Lower the CR on pump gas IMO is just the right thing to do.

[tyr283]

You're comparing a GTX to a GT turbo... that's enough to make up the difference... I don't see how that is a valid comparison at all.

Stock compression on E85 might make slightly more if anything.. but it won't make a lot more vs lower CR on E85... again, it's really not a big of a difference that people think it is. Drop CR and add ignition timing, or leave CR and be knock limited and reduce ign timing (unless your fuel doesn't limit you). The differences really are minimal. Lower the CR on pump gas IMO is just the right thing to do.

I think he's saying the GT made more power at a lower boost than the GTX made

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[e30polak]

I think he's saying the GT made more power at a lower boost than the GTX made

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That is what I'm saying. Also I clearly was referring to e85 with the High CR, as it is the best fuel for that scenario, especially with a turbo. IMO for the money, Dean's e36 has the best power band for the money I've seen. I'd love to see what a stock CR gen 2 6266 with a cut ring, studs, spa manifold and e85 could do. Litemeup's m5 was really impressive with the 6266 on an SPA.

[Butters Stoch]

I think he's saying the GT made more power at a lower boost than the GTX made

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That's no secret. The standard 35r is known to make more power than the gtx35 up to 20ish # on our cars. Same goes with the 6266 gen2 vs gen1. SP did a bunch of testing on Supras with this, they will tell you flat out, if your on pump gas keeping it at a lower to moderate boost setting, the 35r or the gen1 6266 is a better choice and will make more power. Sweet spot of efficiency range maybe.

[NOTORIOUS VR]

I think he's saying the GT made more power at a lower boost than the GTX made

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Didn't catch that the way it was written, but yes... that is not surprising of course.

[tyr283]

That's no secret. The standard 35r is known to make more power than the gtx35 up to 20ish # on our cars. Same goes with the 6266 gen2 vs gen1. SP did a bunch of testing on Supras with this, they will tell you flat out, if your on pump gas keeping it at a lower to moderate boost setting, the 35r or the gen1 6266 is a better choice and will make more power. Sweet spot of efficiency range maybe.

It's been a while since I've looked at the compressor maps but doesn't the GTX outflow the GT all the way across the map? What gives on the GT making more power at lower boost?

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[JOutterbridge]

It's been a while since I've looked at the compressor maps but doesn't the GTX outflow the GT all the way across the map? What gives on the GT making more power at lower boost?

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Compressor efficiency. The 35R has one of the most efficient maps on any turbo Garrett has ever made between 12 and 24psi. Its sick. On Raji and blowing rods, I know my brothers s366 on E85 makes 580whp and similar torque at 20psi. If you really want to run pumo gas on crap 91 octane you need lower compression. If you're dead set on E85 and more power soon then get as high compression as possible. It all depends on what EMU you'll be using and if you're building an flex fuel setup first. If So, you will barely run pump gas. Once you get a taste of E85 and high boost you'll try to fill up on it as much as possible. Pump gas will become an afterthought (trust me)

[tyr283]

Compressor efficiency. The 35R has one of the most efficient maps on any turbo Garrett has ever made between 12 and 24psi. Its sick. On Raji and blowing rods, I know my brothers s366 on E85 makes 580whp and similar torque at 20psi. If you really want to run pumo gas on crap 91 octane you need lower compression. If you're dead set on E85 and more power soon then get as high compression as possible. It all depends on what EMU you'll be using and if you're building an flex fuel setup first. If So, you will barely run pump gas. Once you get a taste of E85 and high boost you'll try to fill up on it as much as possible. Pump gas will become an afterthought (trust me)

My reason for wanting to run pump gas is the fact that E85 isn't available everywhere around me and I don't want to be stuck somewhere unable to find some. I'm still trying to figure out what to do for tuning as well...since I'm OBD1 I think my options are MSPNP, getting two ECU's from RK and switching them out or WAR Chip. I actually think the war chip is really cool but there's no one who seems to tune them

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[pbonsalb]

I think there are switch tunes for obd1. You could have same ECU with 91 and E85 tunes switchable. No E85 near me so I run 93 plus meth but E85 would make more power safely.

GT3582R is a great turbo. I ran one for 5 years on an S52. Made 607/580 Dynojet SAE at 21 psi on 93 plus meth. That was about it though, at least with the 0.82 housing. Very responsive also, at least on the 3.2L. There are probably better turbos today but it's still a good one.

[tyr283]

I think there are switch tunes for obd1. You could have same ECU with 91 and E85 tunes switchable. No E85 near me so I run 93 plus meth but E85 would make more power safely.

GT3582R is a great turbo. I ran one for 5 years on an S52. Made 607/580 Dynojet SAE at 21 psi on 93 plus meth. That was about it though, at least with the 0.82 housing. Very responsive also, at least on the 3.2L. There are probably better turbos today but it's still a good one.

Only switchable OBD1 tune I've found was the WAR Chip

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[pbonsalb]

Check with trm, markert, rk, volloso. I am obd2 so I have not seriously looked into this.