How many PSI do you think i can get away with?

[JNM240]

So after a few trips to the dragstrip and may nights sitting infront of the computer (and laptop) figuring out NISTune, i think i have finally got things working right. Shes boosting GREAT now!

Currently i am pushing 20 PSI with my GT2871R .86 a/r. I have 550cc injectors, a Z32 MAF, and 3" outlet, downpipe and testpipe ( 2 1/2 HKS exhaust however). Engine was built using ACL Calico coated rod and main bearings, Cometic MLS head gasket, and ARP head studs and main studs. AFRs dip down to 10:1 on full boost right now, without ANY knock at all. Wondering, based on this setup, do you think i could get this turbo to 25 PSI safely? Maybe even higher?

I might be trying the track again tomorrow night, all by myself this time, seeing as i still have the slicks on the back. Just wondering if anyone has any warnings about pushing it to 25 pounds of boost. Last time at the track, i couldnt get out of the 16's. Turns out my K value, which i adjusted using the wideband, was still severly out of whack. So the guy i work with who has a 69 Chevelle (350 small block) ran low 14's all night and the smack talk was merciless the next day.

[Cams]

16s? I think your car was pointing the wrong way. j/k

I ran 14.79 with street tires and GT28R at 14psi, so your setup at 20 psi with a good tune should be good for high (maybe mid) 13s.

From what I've read around here that 71R is good for 25+psi, but not quite sure the 550cc would be good enough up there.

[boost_boy]

So after a few trips to the dragstrip and may nights sitting infront of the computer (and laptop) figuring out NISTune, i think i have finally got things working right. Shes boosting GREAT now!

Currently i am pushing 20 PSI with my GT2871R .86 a/r. I have 550cc injectors, a Z32 MAF, and 3" outlet, downpipe and testpipe ( 2 1/2 HKS exhaust however). Engine was built using ACL Calico coated rod and main bearings, Cometic MLS head gasket, and ARP head studs and main studs. AFRs dip down to 10:1 on full boost right now, without ANY knock at all. Wondering, based on this setup, do you think i could get this turbo to 25 PSI safely? Maybe even higher?

I might be trying the track again tomorrow night, all by myself this time, seeing as i still have the slicks on the back. Just wondering if anyone has any warnings about pushing it to 25 pounds of boost. Last time at the track, i couldnt get out of the 16's. Turns out my K value, which i adjusted using the wideband, was still severly out of whack. So the guy i work with who has a 69 Chevelle (350 small block) ran low 14's all night and the smack talk was merciless the next day.

You're running soooo much boost and the car is netting you 16s in the 1320? Something is wrong. You do realize that the Silvias with CA18s run a better time in factory trim? Something is wrong with your tuning or are you just lighting-up the tires throughout the launch, 60ft, etc? I wouldn't be pushing 25psi or even 20psi in your case until you've sorted out your engine management and even your fuel system because those injectors are not enough for the type of air flow you're chasing after. I run 15psi on all of my cars for street use and the power produced is just wicked and that's mainly because of the tuning, not the hardware. If it's not tuned right, it's not going to run right, so work on that tuning and please lower the boost before you mess-up your precious engine.

Dee

[chongs13]

That's strange because I'm running low 13's on the 1320 drag strip with stock internals with apexi ax60 turbo at 14psi on street tires. The ca18det ain't that slow. Just get it tune right, that's what I did.

[mbmbmb23]

What map did you start with as a base map for your tuning? Assuming you are putting out around 350hp your 550's are almost maxed at 43.5 psi base fuel pressure. I'd upgrade to 750's before you cranked it up more.

[Liquid_Neon]

that isnt a half mile track is it? A chevelle should be faster then low 14's in a quarter.

Must be a longer drag strip.

[boost_boy]

What map did you start with as a base map for your tuning? Assuming you are putting out around 350hp your 550's are almost maxed at 43.5 psi base fuel pressure. I'd upgrade to 750's before you cranked it up more.

If anyone manages to get 350hp out of 550cc injectors, you are just a hair away from melt-down.

Dee

[JNM240]

Yeah, car ran a 14.9 at 100mph the first time ever down a dragstrip. Since then, ive put in NISTune and it hasnt been tuned correctly. Until now. My K value was way out of whack, even tho the car ran GREAT at idle and cruising. Under boost, it fell on its face. That seems to be sorted out now, as it actually PULLS HARD under boost again.

The track is a 1/4 mile track. The chevelle is a POS rust bucket. Another guy has a 3rd gen RX7 with a LS1 and a 150 shot running 10.8 at 136MPH.

Went tonight by myself and had issues every pass. First pass: redlighted. Ran a 17.60 at 101.83 with a 5.63 60ft time (cause i paused once the red light went off). Next 2 passes had all kinds of traction problems. It was about 45 degrees out, and i couldnt get the damn slicks hot enough. Wheel spin off the line and throughout second gear both times. Results: 16.45 at 98.02 and 16.34 at 96.06. The car is absouletely booking it once it gets moving, its just now a problem of the drag race: the launch.

[mbmbmb23]

If anyone manages to get 350hp out of 550cc injectors, you are just a hair away from melt-down.

Dee

That's what I was thinking.

http://www.deatschwerks.com/ca...s.php

Second calculator down;

Target HP: 350Injectors: 4BSFC: .55Duty Cycle: 92%

= 549.3cc injectors at 43.5 psi

[mbmbmb23]

Yeah, car ran a 14.9 at 100mph the first time ever down a dragstrip. Since then, ive put in NISTune and it hasnt been tuned correctly. Until now. My K value was way out of whack, even tho the car ran GREAT at idle and cruising. Under boost, it fell on its face. That seems to be sorted out now, as it actually PULLS HARD under boost again.

The track is a 1/4 mile track. The chevelle is a POS rust bucket. Another guy has a 3rd gen RX7 with a LS1 and a 150 shot running 10.8 at 136MPH.

Went tonight by myself and had issues every pass. First pass: redlighted. Ran a 17.60 at 101.83 with a 5.63 60ft time (cause i paused once the red light went off). Next 2 passes had all kinds of traction problems. It was about 45 degrees out, and i couldnt get the damn slicks hot enough. Wheel spin off the line and throughout second gear both times. Results: 16.45 at 98.02 and 16.34 at 96.06. The car is absouletely booking it once it gets moving, its just now a problem of the drag race: the launch.

What RPM are you launching at? Tire pressure? Ive never drag raced before but I'd be willing to bet that launching more controlled at lower RPMs and not wheel spinning would pick up some time on the slip. Look at how they test production cars for Road and Track magazine or other mags....they're not doing burn outs to heat up slicks....they have factory tires and they get lower times with cars you should be faster than.

[float_6969]

Slicks actually make it harder to launch the car. Being turbocharged compounds that.

If you can't get the slicks warmed up, you're better off running a drag radial. Have you checked out the price of a line lock? They're not that much and should allow you to properly warm up those tires.

You need to lean that out. 10:1 is NOT good, and you'll damage the motor by washing the oil off the cylinder walls and toasting the pistons.

You're pushing the limit with those injectors, and any time you push the limit, you're begging for trouble.

Leave the boost alone, get your car ACTUALLY tuned, get a line lock, and make that chevelle look stupid.

[JNM240]

The slicks are actually Hoosier DOT radials, but they are extremely used (3rd or 4th hand by now) and actually have some cord showing near the sidewalls. But they still grip better than my street tires ever would.

I figured that 10:1 wasnt good at all. I didnt record any of my runs last time, since the motor was running great, i was just having traction problems.

Dude with the chevelle's best trap speed was 100 mph, so now at least i have some bragging rights over him (mine was 102). Today i asked him "doesnt the MPH at the end of the 1/4 mile tell you your horsepower? that cant be, because that would mean my tiny 1.8 liter makes more than your built 350 cubic inch, and that just doesnt seem right...."

I agree with you Float, i do need to get it dyno tuned. Problem is i cant really afford that, at $150 per hour im the only one who would have any working knowledge of NISTune and im still not familiar with it at all.