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Discussion Starter #1 (Edited)
Sups Guys,what compression ratio would ya'll recommend running for the 400hp mark 9.0:1 or 9.5:1..im getting away from FJT/ Vitara setup..Im currently running at GT2871R and it made 328hp on 18 psi Tuned on Crome Gold..i just don't like the limp noodle feel out down low, just wanting to up the CR with Weisco's and standard length Eagle rods.
D16z6(this is current Vitara setup)
GT2871R .63ar
Bisi 2.4 cam,spring,retainers,Bisi cam gear
Performer X mani with Omni 68mm TB,Aem fuel rail,B&M FPR
650 Percision Injectors
255 Walboro
mild port work on exhaust/intake runners
PFAB tubular log mani
Turbonectics external 38mm WG.
Arp head studs
Ferrea flat valves
 

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how good is your tuner? if hes good then go with a 9.5-10:1. if he aint well you might want to stick will low comp


IIRC- higher comp you make the same power with less boost, and ittle be more responsive. but you have less room for error, but since your going forged it be more forgiving. make sense?
 

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10.5:1 with quench (which is my goal).

Don't tune on Crome. Spend the money on Neptune. Your engine will thank you. Heck, you may even be able to cure the limp noodle feel without having to rebuild the engine.

Would you be willing to post a dyno chart? The 2871 is my current favorite Garrett turbo.
 

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You have access to E85 down there in GA? Any thoughts in using it? If so, perhaps look at pushing the ratio envelope with 10-11:1! If not, you'll be fine with either 9:1 or 9.5:1.
 

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9.5:1 is probably good middle ground, 10:1 will net you more bottom end torque but may have too high cylinder pressures at high boost, ultimately your tuner will be able to get you the most out of each setup if he's worth his salt... how in love with the 2871 are you? I like them,(t25 housing:TD:)but prefer the 3071, 3076,:wink: go neptune or hondata.
 

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Discussion Starter #9
I'm tryin to find my Dyno sheet to post up for Acid Beaver..im moved recently so its lost somewhere in a mound of paperwork..lol..I have the T3 housing on my 2871R with vband exhaust housing..im thing of 9.5:1 and Hondata or Neptune..Does anybody know tunes with Neptune in Ga?
 

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Discussion Starter #11
Hey Acid,I have heard of Midnite Auto in NYC guy called Morris i think,well i have heard rumors of the shop moving to GA?...i just got home from work and im looking for that Dyno sheet..lol
 

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Discussion Starter #12
Sups Guys,what compression ratio would ya'll recommend running for the 400hp mark 9.0:1 or 9.5:1..im getting away from FJT/ Vitara setup..Im currently running at GT2871R and it made 328hp on 18 psi Tuned on Crome Gold..i just don't like the limp noodle feel out down low, just wanting to up the CR with Weisco's and standard length Eagle rods.
D16z6(this is current Vitara setup)
GT2871R .63ar
Bisi 2.4 cam,spring,retainers,Bisi cam gear
Performer X mani with Omni 68mm TB,Aem fuel rail,B&M FPR
650 Percision Injectors
255 Walboro
mild port work on exhaust/intake runners
PFAB tubular log mani
Turbonectics external 38mm WG.
Arp head studs
Ferrea flat valves
 

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I dunno. I avoid the whole tuner scene around here. I do my own work, so I've not been to a shop in over 10 years. The stuff I can't do is usually shipped to places that can do it for me since it ends up being about the same cost and I know stuff is getting done correctly.
 

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Discussion Starter #15
Thx,Acid..well im gonna sell the FJT/Vitara setup and go forged Weisco's and std length Eagles..I guess im gonna go with Hondata when i change rods piston setup to have a lil better response down low with higher compression..One day i wanna try to tune my self and save money..lol
 

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Wow, very nice torque curve indeed. It climbs right on up there and stays :TU:
 

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9.5:1 is probably good middle ground, 10:1 will net you more bottom end torque but may have too high cylinder pressures at high boost, ultimately your tuner will be able to get you the most out of each setup if he's worth his salt... how in love with the 2871 are you? I like them,(t25 housing:TD:)but prefer the 3071, 3076,:wink: go neptune or hondata.
Ive personaly seen D16's with 10-1 with a 6262 making over 550 at the wheels. How is it too much cyl pressure? Will help spool that 2871 nice. Would be a awesome combo if tuning is up to par.
 

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Ive personaly seen D16's with 10-1 with a 6262 making over 550 at the wheels. How is it too much cyl pressure? Will help spool that 2871 nice. Would be a awesome combo if tuning is up to par.
Not to thread jack but...10-1 leaves little room for error @20psi, even less on pump gas, my last build was around 10.5-1(srps high comps didn't like it much though lol.. most high comp pistons are not turbo friendly...) little torque monster but decided on a much safer 9.5-1 and up the boost on pump gas, I've seen like 12-1 high boost setups that would blow your mind, but setups less that practical for my taste, but to each his own I say. It all comes down to tuning. Its all about controlling cylinder pressures and knowing the knock threshold. Here's my therory: I'm assuming your basing your 550 HP argument on highly modified engines running race fuel.....

There are sound scientific reasons why there are no factory 10 to 1 CR turbocharged engines which produce specific outputs of 175 hp/L. In fact, there is NO production, piston, automotive engine which I am aware of which can achieve a specific output of this level on 92 octane pump fuel anywhere. Despite this fact, many people try to do this with expensive results. High compression ratios and high boost simply don't mix on pump fuel. If you try this, you will either be unhappy with the results or blow up the engine. When I say production engine, I mean one that you can buy off the showroom floor, no modifications, with the factory warranty intact. HP to be tested on a proper engine dyno, not on a chassis dyno with phantom flywheel correction factors applied. If Toyota, Honda or Ford could do this with factory reliability, don't you think that they would? As discussed in some of the reference articles above, set reasonable hp goals and modify the internal components as required to obtain these levels reliably. Be aware that many Japanese spec engines are designed to run on 98-102 octane fuel in their home markets. These engines will not be able to run the same boost levels on North American 92 octane fuel. Expect lots of detonation or spark retard if you attempt this.
As mentioned above, TE is affected by CR and ignition timing. As the timing is retarded, PCP is developed later in the cycle. This allows more energy to be lost through conduction into the water jackets because the piston is further down the bore and the rod has a less advantageous angle on the crank pin to deliver force to the crankshaft. Retarded timing also raises the exhaust gas temperature considerably. This raises the thermal stress on the pistons, spark plugs, valves, exhaust system and turbocharger. In severe cases of retarded timing, the mixture is still burning when the exhaust valve opens. Because turbochargers are driven by the energy in the exhaust stream, high EGTs caused by retarded timing produce so much energy at the turbine that even a fully open wastegate cannot control the boost pressure. All in all, retarded timing is counterproductive to producing an efficient, durable, powerful engine.

Realistically if you wanted to get to the 400HP mark it just would be easier for your tuner and your engine if you had a better flowing turbo/manifold. The gt28r and gt30r @18psi are a world apart power wise IMHO , gt28r can reach 400 but probably out of its efficiency, charge temps can spike, whereas a gt30r could reach those goals easily with your motor with little to no lag vs the gt28r, and possibly on pump gas...just my .02.........
 

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The production argument is weak in my opinion. When's the last time you saw a production motor in our price segment that was forged from top to bottom? Production cars are designed to be sold in a mass market and therefore they allow for a LOT of breathing room when it comes to design. The same car tuned for this area will have a tune different than if it resided on the left coast. IMO unless you're drag racing big power is useless.

You have an awesome power curve with lots of USABLE power. Wanna make it better? You have e85 stations all over the place in Georgia. Bump your compression, get e85 safe fuel lines and have some fun.
 

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Not to thread jack but...10-1 leaves little room for error @20psi, even less on pump gas, my last build was around 10.5-1(srps high comps didn't like it much though lol.. most high comp pistons are not turbo friendly...) little torque monster but decided on a much safer 9.5-1 and up the boost on pump gas, I've seen like 12-1 high boost setups that would blow your mind, but setups less that practical for my taste, but to each his own I say. It all comes down to tuning. Its all about controlling cylinder pressures and knowing the knock threshold. Here's my therory: I'm assuming your basing your 550 HP argument on highly modified engines running race fuel.....

There are sound scientific reasons why there are no factory 10 to 1 CR turbocharged engines which produce specific outputs of 175 hp/L. In fact, there is NO production, piston, automotive engine which I am aware of which can achieve a specific output of this level on 92 octane pump fuel anywhere. Despite this fact, many people try to do this with expensive results. High compression ratios and high boost simply don't mix on pump fuel. If you try this, you will either be unhappy with the results or blow up the engine. When I say production engine, I mean one that you can buy off the showroom floor, no modifications, with the factory warranty intact. HP to be tested on a proper engine dyno, not on a chassis dyno with phantom flywheel correction factors applied. If Toyota, Honda or Ford could do this with factory reliability, don't you think that they would? As discussed in some of the reference articles above, set reasonable hp goals and modify the internal components as required to obtain these levels reliably. Be aware that many Japanese spec engines are designed to run on 98-102 octane fuel in their home markets. These engines will not be able to run the same boost levels on North American 92 octane fuel. Expect lots of detonation or spark retard if you attempt this.
As mentioned above, TE is affected by CR and ignition timing. As the timing is retarded, PCP is developed later in the cycle. This allows more energy to be lost through conduction into the water jackets because the piston is further down the bore and the rod has a less advantageous angle on the crank pin to deliver force to the crankshaft. Retarded timing also raises the exhaust gas temperature considerably. This raises the thermal stress on the pistons, spark plugs, valves, exhaust system and turbocharger. In severe cases of retarded timing, the mixture is still burning when the exhaust valve opens. Because turbochargers are driven by the energy in the exhaust stream, high EGTs caused by retarded timing produce so much energy at the turbine that even a fully open wastegate cannot control the boost pressure. All in all, retarded timing is counterproductive to producing an efficient, durable, powerful engine.

Realistically if you wanted to get to the 400HP mark it just would be easier for your tuner and your engine if you had a better flowing turbo/manifold. The gt28r and gt30r @18psi are a world apart power wise IMHO , gt28r can reach 400 but probably out of its efficiency, charge temps can spike, whereas a gt30r could reach those goals easily with your motor with little to no lag vs the gt28r, and possibly on pump gas...just my .02.........
Arny, I mean this in a friendly way, but STFU.

Your post shows that you know jackall about the GT2871R.

Also, how is 9.5:1 static compression ratio safer than 10:1? How much is that different. Don't make me do math . . . Please don't make me do the math . . . I hate math. I have, however, done enough of these calculations to know that the difference in STATIC compression ratio on basically the same engine is significant, but not terribly large.

What you are alluding to in your post, including the cut and pasted section in the middle (it reads like it was cut and pasted, in any case), is that pump gas has a certain upper limit on pressure that the fuel can take before it auto-ignites in the presence of oxygen.

What is that upper limit? If you can't answer that, then you don't know enough to say "This compression ratio is bad in this engine whilst turbocharging it."

For a more practical rebuttal of your load of nonsense, look at home many stock VTEC B-series engines run around with 3-400WHP. They are all between about 10 and 10.5:1 SCR engines. They don't blow up running pump gas if tuned right.

How is a D-series engine, with upgraded rods and pistons going to be anywhere near the auto-ignition conditions of pump gas with a smaller bore, typically less VE on both the intake and exhaust and most other things being similar (turbo, intercoolers, etc)?

Guess what? None of that really matters, since the SCR of an engine has very little to do with how it runs. I consider Cams the most important part of the engine. A cam or cams can be used to manipulate the dynamic compression ratio in the dangerous ranges of engine operation. Above that point, if the ignition advance is appropriately applied, the intake charge is cooled well enough, and enough fuel is supplied, the engine is going to be more efficient overall with a higher static compression ratio, transferring more power to the wheels per unit of fuel.

E85 allows for more power to be made from the same engine because of factors that most people have no clue about. The typical idiot's view of E85 is that you can run more timing and make more power. Ugh . . . Anyway, E85 burns slower, cools the intake charge more (too?) efficiently, and has a much, much higher autoignition threshold. All those factors allow for an engine using E85 to develop more power with a wider tuning window than most pump gas. That's if you can run it without issues.

To sum up:
-The GT2871R comes in a wide variety of trims and has as much power potential as older GT30 models.
-Pump gas is good for power levels well past what is practical for something driven on the street in a FWD, traction limited vehicle.
-Ignition timing optimization for different fuels has to do with BURN RATES not power potential. (Gasoline mixes need less ignition timing to make maximum torque because it burns faster. Alcohols burn slower (and cooler), necessitating more ignition advance to develop maximum torque than that of a comparable gasoline powered engine.)
-E85 "makes more power" for a bunch of reasons that has very little to do with timing and mostly to do with the very different chemical boding that occurs in alcohols than other long chain hydrocarbons.
-Arny's post had very little to do with what the OP was asking about.
-The OP will make more power with his current setup with higher compression, decrease spool time, increase efficiency, increase favorable throttle response, and get rid of junk engine management for something that will likely yield more power and a more reliable engine.
-The dynamic compression differences in an engine with 9.5:1 SCR and 10:1SCR are minimal. The difference between 8.something:1 and 10:1 will be phenomenal, and doing very good things for the feel of the engine, which is what the OP wants.
 
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