GavinL Posted October 13, 2003 Share Posted October 13, 2003 My car went on the Thor dyno at Santa Pod this weekend......thanks Pete Just a note of caution, my car is running in true twin mode and there was a sudden drop from 14.7 AFR to 10.2 AFR on full boost before settling back down to 12.5 AFR. An AFR of 10.2 is not really ideal even for just a few hundred rpm. For info my car has 550cc injectors, FSE valve, Walbro pump and Hybrid turbo's. I wouldn't like to say that this may happen to your car with the TTC mod but getting your fueling checked with a wideband is a must. Link to comment Share on other sites More sharing options...
eyefi Posted October 13, 2003 Share Posted October 13, 2003 u had an afr of 14.7 on boost? Link to comment Share on other sites More sharing options...
GavinL Posted October 13, 2003 Author Share Posted October 13, 2003 Originally posted by eyefi u had an afr of 14.7 on boost? no 14.7 low rpm to 12.5 on full boost drop to 10.2 between 4k-4.5k on the way up to full boost Link to comment Share on other sites More sharing options...
eyefi Posted October 13, 2003 Share Posted October 13, 2003 ah right, so it went rich at the transition point. mine doesnt do this, but its not stock ecu. why do u think its the parallel conversion? Link to comment Share on other sites More sharing options...
Tannhauser Posted October 13, 2003 Share Posted October 13, 2003 I thought a lower ratio meant the mixture was leaner. Isn't Gavin saying that the car was running lean, not rich, for a little while. And lean = danger for the engine? Link to comment Share on other sites More sharing options...
eyefi Posted October 13, 2003 Share Posted October 13, 2003 lower afr number = richer fuel condition Link to comment Share on other sites More sharing options...
mawby Posted October 13, 2003 Share Posted October 13, 2003 AFR would be Air to Fuel Ratio, so the higher the figure the more air in the mixture. My dyno results had the following... RPM = AFR 2000 = 14.9 2500 = 14.0 3000 = 13.5 3500 = 13.0 4000 = 11.4 4500 = 11.0 5000 = 10.8 5500 = 10.6 6000 = 10.8 6500 = 11.3 6800 = 10.8 Does this sound ok? Link to comment Share on other sites More sharing options...
Tannhauser Posted October 13, 2003 Share Posted October 13, 2003 I knew there was some reason I don't post in the technical section. Of course, you're right. So what is the problem with running so rich, albeit briefly? Link to comment Share on other sites More sharing options...
GavinL Posted October 13, 2003 Author Share Posted October 13, 2003 Originally posted by eyefi ah right, so it went rich at the transition point. mine doesnt do this, but its not stock ecu. why do u think its the parallel conversion? Yes I think the big change in boost pressure caused my fueling to behave erratically. Equally a fuel system not up to the job, tired pump, crappy regulator might not be able to keep up with demand and run lean Link to comment Share on other sites More sharing options...
Steve W2 Posted October 13, 2003 Share Posted October 13, 2003 You technical guys will have to humour me here because I'm not the sharpest tool in the box but why does the AFR change at different engine loads? Surely the air requirement (of the engine) is based on the stoichiometric air requirement of the fuel which does not change. Does the engine require an excess air requirement at low RPM? Link to comment Share on other sites More sharing options...
Matt Harwood Posted October 13, 2003 Share Posted October 13, 2003 Gavin, was that on every run, or just the first? - Reason for asking is that the true twin thing doesn't work from start-up, you have to have been over the point where the second turbo would normally come in before it's activated properly. I'm not sure why this is, but it may be something to do with pressuring the system first... 4000-4500 is where the 2nd would normally be, maybe the ecu was trying to give a quick squirt as the 2nd would normally appear Link to comment Share on other sites More sharing options...
GavinL Posted October 13, 2003 Author Share Posted October 13, 2003 Originally posted by Matt Harwood Gavin, was that on every run, or just the first? - Reason for asking is that the true twin thing doesn't work from start-up, you have to have been over the point where the second turbo would normally come in before it's activated properly. I'm not sure why this is, but it may be something to do with pressuring the system first... 4000-4500 is where the 2nd would normally be, maybe the ecu was trying to give a quick squirt as the 2nd would normally appear All runs Matt, we did charge the pressure tanks before we started. Link to comment Share on other sites More sharing options...
pulse Posted October 13, 2003 Share Posted October 13, 2003 I don't know if it helps with your comparisons, but below is my AFR for a stock J-spec (which may or may not have problems, I don't know). http://www.web-axis.net/~pulse/dyno/afr.jpg -p Link to comment Share on other sites More sharing options...
eyefi Posted October 13, 2003 Share Posted October 13, 2003 gav, mawby can u post the graphs? mawby ys sounds totaly different to pulse's and gav, yrs sounds different to both of em. Link to comment Share on other sites More sharing options...
THOR Racing Posted October 13, 2003 Share Posted October 13, 2003 The issue was not the 10.2 it was the 12.5 AFR at high load. ideally you'd be looking at 11.5 AFR on a turbo car on full load. 12.5 was a little too lean for WOT. 10.2 is a little rich but not rich enough to worry about. I wouldn't worry unduly unless it was below 10 and in the 9.5's before I'd have to take action. As a seperate issue...... A few of the Supras were showing signs of late 2nd turbo. A large tranistional drop of pressure between single and twin turbos spooling. About a 500rpm lag in the pair coming on line. Now this was seen as a noticable dead spot in the torque and also a concequential drop in fueling by the ECU. (These were stock cars compared with stock cars) This appeared quite a common fault. I have all the plots and if everyone is O.K. and can send me a photo or your car and reg number to my email address ([email protected]) I'll add you to the hall of fame and you'll all be able to compare different specs of Supras with one another. (Better still if it's pictures of them on the dyno) It was nice to see so many stock cars. I have a good baseline of Jap spec and UK spec cars now. When overlaid on top of modified car plots you really see what mods work. Regards Pete Link to comment Share on other sites More sharing options...
pulse Posted October 13, 2003 Share Posted October 13, 2003 Originally posted by TRL Performance As a seperate issue...... A few of the Supras were showing signs of late 2nd turbo. A large tranistional drop of pressure between single and twin turbos spooling. About a 500rpm lag in the pair coming on line. Now this was seen as a noticable dead spot in the torque and also a concequential drop in fueling by the ECU. (These were stock cars compared with stock cars) This appeared quite a common fault. Hi Pete, This appeared on my graphs too.. If you remember mine (Black, K*** RGP), you said it looked like it might be leaking boost a little or similar, and 2nd turbo a bit late. Did you see others with the same issue? Can I stop panicking? I'm going to get it checked out anyway, but would be nice (for me, not others:)) to hear I'm not alone. I have all the plots and if everyone is O.K. and can send me a photo or your car and reg number to my email address ([email protected]) I'll add you to the hall of fame and you'll all be able to compare different specs of Supras with one another. (Better still if it's pictures of them on the dyno) My reg is above Feel free to add it, I took loads of pictures of mine + Millhouse's while on the Dyno (they're on his camera), so as soon as he gets them off I'll send you some pics too. Cheers -p Link to comment Share on other sites More sharing options...
GavinL Posted October 13, 2003 Author Share Posted October 13, 2003 Originally posted by TRL Performance The issue was not the 10.2 it was the 12.5 AFR at high load. ideally you'd be looking at 11.5 AFR on a turbo car on full load. 12.5 was a little too lean for WOT. This is being investigated, thanks Pete. Link to comment Share on other sites More sharing options...
Steve Cargill Posted October 13, 2003 Share Posted October 13, 2003 Originally posted by TRL Performance A few of the Supras were showing signs of late 2nd turbo. A large tranistional drop of pressure between single and twin turbos spooling. About a 500rpm lag in the pair coming on line. Now this was seen as a noticable dead spot in the torque and also a concequential drop in fueling by the ECU. (These were stock cars compared with stock cars) This appeared quite a common fault. Since the rebuild and S3 hybrids this has become very obvious in my car. The old setup pulled smoothly, now there is a hugh flat spot/dip as the 2nd comes on. Sometimes it's kicked down into this dead spot and there is just nothing there!!! I understood this was a featuew of the hybrids. Link to comment Share on other sites More sharing options...
eyefi Posted October 13, 2003 Share Posted October 13, 2003 Originally posted by Steve Cargill I understood this was a feature of the hybrids. nice feature Link to comment Share on other sites More sharing options...
Steve Cargill Posted October 13, 2003 Share Posted October 13, 2003 Originally posted by eyefi nice feature I've just had a search and can't find the post about this, it was discussed a littel while ago. Something to do with the way the work makes the dip more prominent. Link to comment Share on other sites More sharing options...
Guest Terry S Posted October 14, 2003 Share Posted October 14, 2003 Sorry Guys, didn't read the whole thread. Gav you really want to be about 11.5 at full load. Link to comment Share on other sites More sharing options...
THOR Racing Posted October 14, 2003 Share Posted October 14, 2003 I think some of you missed my point. All Supras (twin sequential turbos) have a pressure drop and lag between single and twin operation BUT some have a more pronounced delay (500rpm) and a greater pressure drop between turbos. So yes it's a common factor in all sequential turbo setups but it appears to be more pronouced in some, seemingly, same spec cars. Regards Pete Link to comment Share on other sites More sharing options...
Guest Terry S Posted October 14, 2003 Share Posted October 14, 2003 Pete, is the issue more pronounced on the UK's than the JDM's? The reason I ask is the 9v/12v thing. I noticed with mine wnen nearer standard that on a JDM the fuel pump switches to 12v as soon as positive boost is made, but I am not sure the UK uses the same method. I remember you being in my car and me showing you the dramatic drop in pressure on the pressure gauge. I am just wondering if the ECU's are doing something a little funky at the transition point. Link to comment Share on other sites More sharing options...
THOR Racing Posted October 14, 2003 Share Posted October 14, 2003 Terry, Might be worth looking into. Maybe at the Dyno Day. The effect was seen on JDM mainly. The UK car and JDM and VVTi all showed differences but the problem in question was between cars of similar mod level and same spec (JDM) Pete Link to comment Share on other sites More sharing options...
Jive Posted October 14, 2003 Share Posted October 14, 2003 Originally posted by TRL Performance It was nice to see so many stock cars. I have a good baseline of Jap spec and UK spec cars now. When overlaid on top of modified car plots you really see what mods work. Regards Pete Pete, nice to meet you and thanks for doing my car - glad everything came out "as you expected" for a stock NA - JSpec Sorry for a slight hijack of a thread here Pete, you said you've got a good baseline for stock j-specs, does this include NA's now? I'm considering doing some mods to get some more power out next year and would be really interested in what's good and what's not? Everything "mod wise" on this forum seems to be aimed at TT's and there's hardly any info for us NA owners Link to comment Share on other sites More sharing options...
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