Built engine GTX2867R - Poor power and flat spot (W/ Dyno Graph and Logs)
1 Attachment(s)
Setup Highlights:
1. There's a flat spot in torque between 5,300 and 6,700 RPM (You can see the car start to recover at 6,300 RPMS) 2. Car is generally under powered for the PSI it's running. Next Steps:
Recent Dyno: https://cimg0.ibsrv.net/gimg/www.mia...e385c7e4da.jpg Log from that pull (full log attached): https://cimg0.ibsrv.net/gimg/www.mia...b602fa2a55.png |
2.5" exhaust is sure as hell not helping. That boost curve seems so bad.
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6 psi @ 4K rpm... someting wong heow.
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0.86 A/R turbine housing. The 0.64 on the 2867R will spool to 20psi much earlier, but will probably fall off more on the high side.
the 0.86 is a poor choice for a non-compounded/twin application. |
1 Attachment(s)
It won't take anymore timing below 6000rpms without knocking? If it will that will help spool a good bit, those 10 degree cells @ 210kpa seem low to me. The boost spike at 5500rpms is definitely contributing to the dip in power from 6000-6500, but it still looks odd. How are you controlling boost?
The 2.5 inch exhaust with cat aren't doing you any favors, but with that turbo at 20psi I think you're right to expect more. Also, a little constructive criticism on the fuel map. You should interpolate the red portion (which will pull fuel) and add fuel in the black portion. At 6000rpms you're going super lean and stumbling at 2-20% throttle and piggy rich at 60-99% throttle. Those boost but not WOT cells are often overlooked and autotune always tends to pull too much fuel from light throttle high rpm cells. Attachment 229855 |
Check cat for meltage/blockage/restriction, bigger exhaust would = more power, dip is likely lack of ignition timing, I would check AFR calibration too. If it won't take more timing without knocking with 8.4:1 and a big a/r turbine, your exhaust sucks or octane is way too low. My 2cents.
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Originally Posted by patsmx5
(Post 1434881)
Check cat for meltage/blockage/restriction, bigger exhaust would = more power, dip is likely lack of ignition timing, I would check AFR calibration too. If it won't take more timing without knocking with 8.4:1 and a big a/r turbine, your exhaust sucks or octane is way too low. My 2cents.
Also, odd as it seems, less fuel helps me spool. |
All, I really really appreciate the feedback. I made a list of recommendations below:
Possible issues:
Thanks again |
Here's a snap shot of the cat.
The second picture is holding the entire pipe above a strong light. I'm going to go drive the car shortly and try and get another log (without getting arrested for the noise). https://cimg1.ibsrv.net/gimg/www.mia...53011a65d3.jpg https://cimg2.ibsrv.net/gimg/www.mia...0e1460a2c7.jpg |
I would actually expect to see a 1000-1500 RPM improvement in the spool. A gtx28R should be between 3500 and 4000 or thereabouts on a well tuned 1.8. The 0.86 is probably helping you right now where you are actually making power.
There looks to be something wrong with your fueling coefficients and/or calibrations. It is most likely either your injector flow or dead time, but it could also be in the MAT, CLT, ... you have idle VE at 115, and your sub 100kpa cells are all too high. I would highly recommend getting this figured out, and when you re-run VEAL, do it with incorporate AFR. It is difficult to evaluate the fuel table as currently configured. |
Originally Posted by Ted75zcar
(Post 1434932)
I would actually expect to see a 1000-1500 RPM improvement in the spool. A gtx28R should be between 3500 and 4000 or thereabouts on a well tuned 1.8. The 0.86 is probably helping you right now where you are actually making power.
There looks to be something wrong with your fueling coefficients and/or calibrations. It is most likely either your injector flow or dead time, but it could also be in the MAT, CLT, ... you have idle VE at 115, and your sub 100kpa cells are all too high. I would highly recommend getting this figured out, and when you re-run VEAL, do it with incorporate AFR. It is difficult to evaluate the fuel table as currently configured. Some quick notes:
https://cimg5.ibsrv.net/gimg/www.mia...eb3daa3812.png |
Here're two pulls from this morning with the mid pipe fully removed from the car.
The only adjustments were:
RED Line: Yesterday's pull with cat still installed BLUE Line: Exact same piece of road as RED line but without cat. GREEN Line: Seemingly flat highway entrance ramp Looks like I'm going catless afterall :facepalm: Maybe i can donate to environmental group so i can sleep better at night? (Although this isn't my DD). https://cimg7.ibsrv.net/gimg/www.mia...a525ef4935.jpg |
Something doesn't make sense. With a lower than actual injector size the REQ fuel goes up and VE goes down.
if you truly are getting 300+ hp it would probably be advisable to get the configuration as accurate as possible and not allow significant errors to be absorbed into the fundamental tuning parameters. The amount of margin you have for error drops substantially at these power levels. |
Originally Posted by Ted75zcar
(Post 1434942)
Something doesn't make sense. With a lower than actual injector size the REQ fuel goes up and VE goes down.
if you truly are getting 300+ hp it would probably be advisable to get the configuration as accurate as possible and not allow significant errors to be absorbed into the fundamental tuning parameters. The amount of margin you have for error drops substantially at these power levels. Additionally: Looking at a few past logs, it's obvious the car likes sub 12.0AFR while spooling. The mid-pipe/cat is now reinstalled so we'll see if I can keep any of that better spool (shown above) by keeping the AFR's down earlier. Will report back later with findings. Thanks again! |
Well if the battery voltage reading is off by ~4V, then you will be pulling ~600usec off the top which has to be made up. Get the voltage reading fixed first ;)
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After putting the mid pipe back on the car, and again playing with AFR, I was right back where I started with power/spool. (My hope was running the car rich was contributing to the better spool)
I had the axle back off the car a few weeks back and it made zero improvement, leading me to believe my issue is entirely related to catalytic converter, and not necessarily the 2.5inch exhaust. At this point I can:
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Update: going with the "less cheap" option and am going to replace the 2.5inch ceramic 300 cell cat, for a 3inch metal 100 cell cat. Hoping to have the car back on the road within a week.
With the cat no longer being an issue, I don't think the exhaust as a whole will be a restriction and the car should be able to spool quicker and hit the goal of 300whp+ much sooner. I'd love to trap 115 mph before the season is out but will settle for 112. Fingers crossed. |
Wait are you installing a 3" mid pipe, and the connecting to your 2.5" axle back?
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The entire exhaust is 2.5". When I remove the axle back, there's no change in performance. When I remove the cat, there's a huge change in performance - the car will actually make more power than desired.
Thus I'm simply replacing the current cat with a much much better flowing one, I have sitting in my garage. That cat happens to be 3inch. Is a 2.5inch exhaust with a 3inch cat ideal? Nope. But I'm not replacing the entire exhaust system nor am I running catless. If it doesn't work for some reason, I'll regroup. |
Originally Posted by Carloverx
(Post 1435228)
The entire exhaust is 2.5". When I remove the axle back, there's no change in performance. When I remove the cat, there's a huge change in performance - the car will actually make more power than desired.
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