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Dyno tuning

An interesting read, to be sure.
I need to convince my youngson to quit messing around, finish the MegaSquirt, and take his turbo'd MkI to the dyno .
Thanks, Dan.

larry
sandiego16v
  ----- Original Message ----- 
  From: Dan Bubb 
  To: scirocco-l@scirocco.org 
  Sent: Sunday, August 13, 2006 4:07 AM
  Subject: Dyno tuning


  LONG, LONG, LONG!!

  Finally decided that it was time to stop farting around and put the nephew's 
  (Mike) car on a dyno and actually tune it.

  Couple interesting things came out of this.
  The first was that we wasted about 5 runs trying to fix the engine running 
  lean at low RPM boost. We kept richening up the lean area at 3500 and below 
  and kept seeing the 4500 RPM range richening up with no change at 3500. Well 
  there's the length of the exhaust pipe and there's about 10 ft of tubing to 
  the dyno's WB and that was essentially delaying the signal about 1000 RPM. 
  5 wasted runs figuring out the dyno WB had a significant delay.

  Once up into the higher RPM ranges the dyno WB was showing leaner running 
  than Mike's Innovate LC-1 WB by about .5 AFR so we used that as calibration 
  which was the point of using the dyno WB in the first place. So, basically 
  we went back to Mike's original map that had a very consistent AFR from his 
  tuning efforts, richened the whole boost portion of the map by .5 AFR and 
  ditched the dyno WB. So, something to keep in mind and the most likely 
  reason that dyno runs always seem to start off lean.

  The second thing was that despite all the effing around with AFR in the 12.5 
  to 13.5 range, we saw no significant difference in power. Richening it up 
  did stop the engine from pinging when boost first came in though. 
  http://i9.photobucket.com/albums/a95/jdbubb/86%20JH%20Turbo/scan0001.jpg 
  That was about as far as we could go with fuel tuning. I figured we were 
  about done cause when we started we had some pinging.

  Mike's using a Cheapass (R) ball and spring boost controller that we cobbled 
  up (works just as good as a Forge manual boost controller though!) and it 
  allows boost to initially rise to 13psi, then brings it back to 10 psi and 
  maintains that fairly well. That's why there's a big hump in the torque 
  curve at 3800. That's also where we had some pinging.

  So, the next thing to try was spark advance. Again, at 3800 and 13 psi we 
  were already, apparently, on the limit. So we progressively added more 
  advance at higher RPM. 1 degree at 4200, 2 at 4800-6200 and 3 at 7000. We 
  did this several times and the progression can be seen here: 
  http://i9.photobucket.com/albums/a95/jdbubb/86%20JH%20Turbo/scan0003.jpg
  Advance at 3600 and below was unchanged, but the engine definitely liked 
  more advance at higher RPM and we were able to bring the high RPM torque up. 
  Advance at 6200 went from 17 to 23 degrees by the time we started pinging 
  again.

  Lastly we tried increasing boost. We had essentially been tuning at 160 kpa. 
  Increasing boost only 1.5 psi brought fairly significant pinging (BTW, you 
  should hear pinging on the dyno. It's almost like the engine's sneezing, but 
  it's a really hard mechanical sneeze ;^) so we started bringing the advance 
  in the 190 kpa range down to compensate. In the end we ended up with 
  virtually the same power we had at 10 psi boost since we had to pull so much 
  advance out. So, that was that. Back to 10 psi boost and call it a day.

  Also of interest is watching an engine on the dyno. They move around a LOT!! 
  Towards the end of the day we could almost tell how well the run had gone 
  just by watching the engine position. No top end, you could see it relaxing 
  in the mounts! Last run, it was leaned back all through the run. ;^)
  First and last run comparison: 
  http://i9.photobucket.com/albums/a95/jdbubb/86%20JH%20Turbo/scan.jpg

  Eighteen runs, $200, we'd learned a few things, got a shitload of data and 
  picked up 13 peak hp with an even bigger difference above 5400. 186whp @ 
  5400 on 10 psi boost and 220 lb-ft @ 3800. Maybe not huge numbers but this 
  is an incredibly streetable turbo. Where before it was all about using the 
  midrange and shifting early, now it's still pulling strong at 6500. ;^)
  Imagine Mike sneaking up on sooo many unsuspecting suckers driving this: 
  http://i9.photobucket.com/albums/a95/jdbubb/86%20JH%20Turbo/100_0759.jpg 
  What a kick in the butt to drive!!

  What's next? Mike's engine apparently isn't very detonation resistant. Gotta 
  get around that and run some more boost.

  One of these days I'll have more power than my nephew! :^(

  Dan




   




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