nakagusukumike Posted April 8, 2009 Share Posted April 8, 2009 2.8L HKS RB26 twin N1's 720cc/2 core ARC My tuner has checked my MAP settings, timing, A/F, everything looks fine... But I'm getting 1050C EGT's in 3rd gear @ 0.8bar of boost. Funny thing is, Turn the boost up to 1.4Bar and the EGT's are 950/1000. Still high I know but, is it possible that the turbines are just too small and are choking the motor thus causing high EGT's. We've troubleshot EVERYTHING and my tuner knows his ♥♥♥♥. Garage Speed Factory in Okinawa. Also, Anyone got dyno charts for twin 2530Kai turbines? Can't find any info on them and I'm considering buying. Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted April 8, 2009 Share Posted April 8, 2009 OK, I am no expert or professional, but I have been spending a lot of time staring at compressor maps for the last couple of weeks. Nice car by the way! Is it an R32 with an N1 motor or what? Modified much? The link in your sig requires a login to view pics. Here is what I am trying to comprehend about compressor maps. It seems like the way the islands work is: if you are above, below, left or right of the higher islands, you're producing more heat. A possible explanation I am thinking of is that the center of your highest efficiency island - where you'll produce the least heat - is closer to 1.4 Bar than 0.8 Bar. I looked around for a long time for compressor maps of your turbos (it seems like they are T25s with 49 trim and 0.48 A/R, similar to the CA18DET turbo, and several others), couldn't find a good map though. Not many maps for the T25s. Anyway, for example: (I picked this map because it seemed to best illustrate my point) Therefore, in this map, draw horizontal lines across the map at different boost levels, we'll take the 2 boost levels you ran at, 0.8 Bar and 1.4 Bar. 1. At 1.4 Bar, (a pressure ratio of 2.4), as your motor climbs in RPMS, the airflow plot moves from left to right on the map. As it does it goes through almost the widest part of the highest efficiency island. So, it spends a lot of time in an efficient region of the compressor map where the compressor produces the least amount of heat. 2. At 0.8 Bar, (a pressure ratio of 1.8), the flow plot just barely cuts through the bottom tip of the highest efficiency island. So it is spending less time in the part of the map where the turbo is producing the least amount of heat, and more time in the part of the map where the turbo is less efficient and therefore producing more heat. What I am not sure I understand is this: If the turbo is in an area of lower efficiency, does that mean it is producing more heat, even if you are running less boost (you would think this would put less stress on the turbo)? Or does efficiency mean something else, not necessarily more heat? Maybe I am just unnecessarily associating/equating efficiency with heat production. It's interesting to me how different turbos have different efficiencies at different boost levels, like the GT ball bearing turbos - some of them lose efficiency above 30psi (2 Bar), others above a mere 18psi (1.25 bar). Of course it is the smaller ones that lose efficiency at lower boost, but even in similar sized larger turbos (GT35s etc) different compressors seem to have noticeably different boost levels at which they are most efficient. Some like 15-20 psi, and others like 25-30 psi. Quote Link to comment Share on other sites More sharing options...
TimZ Posted April 12, 2009 Share Posted April 12, 2009 2.8L HKS RB26 twin N1's 720cc/2 core ARC My tuner has checked my MAP settings, timing, A/F, everything looks fine... But I'm getting 1050C EGT's in 3rd gear @ 0.8bar of boost. Funny thing is, Turn the boost up to 1.4Bar and the EGT's are 950/1000. Still high I know but, is it possible that the turbines are just too small and are choking the motor thus causing high EGT's. We've troubleshot EVERYTHING and my tuner knows his ♥♥♥♥. Garage Speed Factory in Okinawa. Also, Anyone got dyno charts for twin 2530Kai turbines? Can't find any info on them and I'm considering buying. The compressor efficiency can effect the EGTs, but as I recall elevated intake air temps should translate directly to the EGT (i.e., elevating the intake air temp by 50deg should elevate the exhaust temp by ~50 deg, all else equal). So, in order for this to be the main problem the intake air temps would have to be pretty high. Which begs the question - what are the intake air temps? While it sounds like you trust your tuner, it would still be helpful to know some details such as ignition timing, air temps, AFR, C/R, cam timing/specs, fuel type, etc. This would enable us to ask more intelligent questions and give more intelligent answers. In my experience (L-series, not RB), I didn't start seeing high EGTs until I went to a very large turbine housing (GT42R with 1.15 AR). Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 12, 2009 Author Share Posted April 12, 2009 Bumped my CAS counterclockwise a bit and that fixed it. EGT's are now 950 peak after a full 1st through 4th runout. Timing was not spot on, but it wasn't knocking. Quote Link to comment Share on other sites More sharing options...
TimZ Posted April 12, 2009 Share Posted April 12, 2009 Bumped my CAS counterclockwise a bit and that fixed it. EGT's are now 950 peak after a full 1st through 4th runout. Timing was not spot on, but it wasn't knocking. So you are saying that you advanced the timing, right? Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted April 13, 2009 Share Posted April 13, 2009 I've always read that it is normal for EGT's to be over 1400 degrees F) , and if they aren't that high you're leaving power on the table - running too rich or timing off. 1900_ degrees sounds like a bit much if you're not racing for sure. This is for gasoline - not diesels, which run a lot lower temps. which is why the variable vane turbos don't work very long behind gas engines as they do with diesels. Quote Link to comment Share on other sites More sharing options...
TimZ Posted April 13, 2009 Share Posted April 13, 2009 I've always read that it is normal for EGT's to be over 1200 degrees, and if they aren't that high you're leaving power on the table - runnubg too rich or timing off. This is for gasoline - not diesels, which run a lot lower temps. which is why the variable vane turbos don't work very long behind gas engines as they do with diesels. He's talking Celsius, not Fahrenheit. 1050C is over 1900F. That's pretty hot. Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 13, 2009 Author Share Posted April 13, 2009 Yes I advanced the timing, and I'm talking in Celsius. With the timing advanced slightly I found a good balance of peak EGT's around 950/925 @ 1.4 bar with peak knock of 29. Ran like a raped date last night. I'll have to check my cold air temps next time I'm out. This is a street race car in Okinawa. It comes out of the driveway 2 nights a week. House -> Drive to Location -> Have fun at location -> Drive home. Repeat. After carefull research for months and months I'm thinking about this: 2530Kai Twins with an HKS V-Cam. Looking for about 125-175HP more than what I've got now and a FAT FAT dyno curve. Quote Link to comment Share on other sites More sharing options...
TimZ Posted April 13, 2009 Share Posted April 13, 2009 Yes I advanced the timing, and I'm talking in Celsius. With the timing advanced slightly I found a good balance of peak EGT's around 950/925 @ 1.4 bar with peak knock of 29. Ran like a raped date last night. I'll have to check my cold air temps next time I'm out. This is a street race car in Okinawa. It comes out of the driveway 2 nights a week. House -> Drive to Location -> Have fun at location -> Drive home. Repeat. After carefull research for months and months I'm thinking about this: 2530Kai Twins with an HKS V-Cam. Looking for about 125-175HP more than what I've got now and a FAT FAT dyno curve. Okay, so now we have established that changing the timing did in fact help - in this case it wouldn't hurt to review the timing map Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 13, 2009 Author Share Posted April 13, 2009 timing map is fine. It was the CAS that got moved, the timing in the powerFC didn't change. But of course it needs the CAS to be set properly for the map to line up right. Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 14, 2009 Author Share Posted April 14, 2009 EGT's are now around 800/850. Air temp peak was 55. Runs like an analy raped date. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 15, 2009 Share Posted April 15, 2009 Just a followup for everyone. Any tuner who "knows his !$%@" should know that not enough timing is the first issue to look at with high EGT's on a turbo car. It sounds like it just needed a tweak. Good to hear it's getting ironed out. EGT gauges are popular for mildly tuned modern EFI cars as the EGT's will change (go up) when the ECU pulls timing due to detonation. Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 15, 2009 Author Share Posted April 15, 2009 My tuner does know his ♥♥♥♥. My CAS is going out, but thanks for the comment. If there was any failure point between the situation and your understanding of it, it was probably due to my written explanation of the situation. This is one case where I developed a troubleshooting matrix that had repeatable results but only in a small sample of time. Over the larger sample of time the troubleshooting matrix fails due to inconsistent outcomes which in the end was due to an electronic sensor failure. Sorry I failed to include every iota of detail in the thread, I was more interested in beating the ♥♥♥♥ out of my car Cheers All! Ran out 2nd and 3rd with the following peaks: knock 29 air 58C boost 1.5bar egt 850C Guess I need to update my signature picture Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 15, 2009 Share Posted April 15, 2009 My tuner does know his ♥♥♥♥. Gah, I didn't say anything against your tuner. Just was posting as "a followup for everyone" that it makes a good example of diagnosing turbo tunes. Quote Link to comment Share on other sites More sharing options...
nakagusukumike Posted April 15, 2009 Author Share Posted April 15, 2009 absolutely. And I just wanted to say that I probably didn't explain the whole situation accurately. Cheers! Good to know though! Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted April 17, 2009 Share Posted April 17, 2009 Love the color to death, by the way. I painted one of my old cars (CT9A Evo) a similar color with just a hint of a purple cast at an angle. Drove up to a circuit car show and won best paint. Quote Link to comment Share on other sites More sharing options...
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