disappointing 2871r results

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broken40s
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disappointing 2871r results

Post by broken40s »

setup:
stock crank and rods
balanced rotating assy
supertech pistons
gt2871rs @ 21 psi
fmic
750 injectors
bc 264 cams
nistune
93 octane crap ethanol gas
q45 diff

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i was a little disappointed. i expected more, quite a bit more. i adjusted my fuel map inbetween runs. i got it at about 12 now. i increased my timing afterwards since it was pretty conservative. imma try and go back and do a little tuning next month. we'll see what happens.
Last edited by broken40s on Sat Jul 23, 2011 11:20 pm, edited 1 time in total.
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Post by 8-bit »

the image is too small to read any of the numbers....
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Post by Berserker »

Hmm that turbo should not fall off on top like that, do you see ur psi dropping on top end?
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broken40s
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Post by broken40s »

8-bit wrote:the image is too small to read any of the numbers....
shows up fine on my 10" screen
Berserker wrote:Hmm that turbo should not fall off on top like that, do you see ur psi dropping on top end?
it peaks at like 21 but doesnt go below 19
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Post by superDorifto »

8-bit wrote:the image is too small to read any of the numbers....
agreed, blurry as ****, what did you actually lay down?
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broken40s
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Post by broken40s »

superDorifto wrote:agreed, blurry as ****, what did you actually lay down?
i'll see if i can get a better pic up tomorrow. made 288 whp, 327 tq
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Post by sh1tsweak »

wow that does fall off pretty bad. no boost leaks? are the cams degreed? whats your timing look like?
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Post by Berserker »

Yeah that falls off worse then stock s14 cams.
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Post by all shal perrish »

my guess is the cams are not degreed correctly and that is causing your terrible power drop off
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Post by broken40s »

im using stock cam gears, so im sure it could benefit from some adjustable ones, but they're right on. runs too smooth for it to be off a tooth. wastegate line comes from the plenum, so if there is a boost leak, it shouldnt affect it too much, i wouldnt think, and like i said it never went below 19psi. intercooler pipes are one piece to try and alleviate multiple couplings and i checked them for leaks with water overnight when i welded them up. intake vacuum is 20 in/hg at idle. imma go back after i get paid again and do a little bit of tuning. i got andy from autovaughperformance giving me some advice on it. after the dyno, when i advanced timing it "felt" quite a bit faster, since it was a pretty conservative timing map. i'm monitoring knock with an safc2, prolly not the best tool, but its what i got. i'll post updates as i get them.
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Post by NateDogg »

I would expect 330-350whp on that setup at 19 psi.

The jagged dyno plots look like possible spark blowout and or timing way too retarded. Try closing the plug gap down .005 and see if that makes it run smoother up top. If not, your timing needs adjustment. Do you know the peak timing you are getting..

Just FYI I picked up 50whp with 4 deg more timing.

So as they say "it's all in the tune"
Last edited by NateDogg on Mon Jul 25, 2011 11:29 am, edited 1 time in total.
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Post by redpotatoes »

The numbers seem low for that kind of boost, I am at 14.5 psi with 232/232 cams and making 305/320.
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Post by zenki-des »

its possible you could have boost leak but not able to pick up on it due to having your waste gate ran to you plenum. you could be seeing 20psi on the gauge but your turbo is struggling to keep up, you should run a line from your charge pipe to your turbo. inefficient boost feels way different from efficient boost turbo could be work at 35psi trying to make 20psi
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Post by broken40s »

i'm pretty sure theres no boost leak. i've checked the couplings for tears and the pipes for leaks before i installed them. plugs are gapped to .025. dyno looks horrible like its breaking up, but it actually runs smooth all the way up. the tune im running was originally for a t3/t4 setup at 15 psi that i've been manipulating, so like i keep saying i'm pretty sure its pretty conservative for my lil turbo. i'm anxious to go back to the dyno after making some adjustments. imma steal my fiancee's ipod and put the dynolicious app on it for now. i was expecting about 360 whp, but it did at least give me a baseline to see whats up and where to go from here. at least i can make adjustments myself and dont have to send off my ecu.
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Post by adamky »

all shal perrish wrote:my guess is the cams are not degreed correctly and that is causing your terrible power drop off
Yep. Bonomoskat dyno'd his car with BC cams and stock gears and was very disappointed with the results. He then degreed the cams and picked up a whole lot of power... 50 whp and almost 70 wtq in some places. See here: viewtopic.php?t=43575
There was also seanc, who dyno'd his car before/after installing BC V2's and had the same exact curve... he actually lost about 4 hp and gained 4 wtq: viewtopic.php?p=180360&highlight=#180360
broken40s wrote:im using stock cam gears, so im sure it could benefit from some adjustable ones, but they're right on. runs too smooth for it to be off a tooth.
BC cams are well known for being way off from the cam card, even when installed in stock positions. And we're not talking about a degree or two here. We're talking about 10 degrees off. This has been confirmed several times by members of this forum.

BC cams with stock cam gears perform no better than stock S13 cams. I've been on this forum for a while now and I've seen it time and time again.
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Post by turbonola »

those numbers are way low, i dyno'd 346who 373wtq @15psi on a gt2876r
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Post by p00t »

Do you know what size gt2871 you have? Turbine AR and Compressor Trim? Smallest gt2871 vs gt2876 flows 10 less lb/min, pretty significant.

If you have the 64 AR exhaust you might want to try s13 cams in stock position or degreeing the BC's. The less overlap the better for small turbines.
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Post by broken40s »

p00t wrote:Do you know what size gt2871 you have? Turbine AR and Compressor Trim? Smallest gt2871 vs gt2876 flows 10 less lb/min, pretty significant.
turbine ar is .64, and compressor trim is 52.
p00t wrote:If you have the 64 AR exhaust you might want to try s13 cams in stock position or degreeing the BC's. The less overlap the better for small turbines.
i think the next mod is to get some gears and degree the BCs.

also, i could be completely wrong, but what do you guys think about my q45 diff causing the lower numbers?

i went back to the dyno today to try and tune it a little better, and this is the best i could get with out any knock. almost 40 hp improvement.

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Post by p00t »

Wow, that looks a lot better, I guess it was all in the tune!

There's no significant difference with the gearing, if anything it will show slightly higher numbers like when you do a pull in 3rd vs 4th.
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Post by adamky »

Much better. I would still look into degreeing those cams if I were you. It would really help to keep the power from dropping off.
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Post by NateDogg »

Nice work!

Post a screenshot of your timing map.

I usually add a degree at each RPM box above 5500.
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Post by spartanmisfit »

Nice adjustments. I ran into the same problems with my s14.
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broken40s
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Post by broken40s »

NateDogg wrote:Nice work!

Post a screenshot of your timing map.

I usually add a degree at each RPM box above 5500.


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next, imma get some adjustable cam gears and some meth/water injection.
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Post by Walperstyle »

all shal perrish wrote:my guess is the cams are not degreed correctly and that is causing your terrible power drop off
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