slownrusty Posted May 31, 2009 Share Posted May 31, 2009 Guys - A few weeks ago I went to the dyno with my bone stock grandpa owned low mileage '83 5speed 280ZX Turbo. I pulled this on the dyno, the car was making 6psi of boost: I then had a beautiful mandrel bent 3.5in exhaust made for me by the very talented Jon Vigil and used a Burns muffler. The Good News: Car felt fantastic with the new exhaust so and went back to the dyno today to see how much hp just adding the exhaust alone gave me..I was surprised I picked 25whp (!!) and 11wtq (ft.lbs)..with the new system the boost crept up 1psi to 7psi. I was actually shocked and pleasantly surprised so thats about 30 flywheel hp and 12 flywheel torque gain. Goes to show you what a difference a well thought out and designed system will yield. The Bad News: I am still having a problem with the car in that it starts running lean from 4,500 to redline (look at my AFR curve), it goes from the mid 10s to mid 12s. Almost as if there is a fuel delivery problem. I changed the fuel pump to a replacement Carter unit thinking that the factory pump was on its last legs, but that did not change anything. Any ideas? I am going to next try: 1) Blowing out the fuel lines, make sure there are no clogs. 2) Change the fuel filter again 3) Install a fuel pressure gauge to see if the pressure drops as the rpms and load on the motor climbs. 4) Clean the wiring at the fuel pump Should I try another AFM and ECU? What about the factory FPR? Any other thoughts? I am still working on my white ZX Turbo trying to finish it up, made some great progress with it this weekend. Thanks - Yasin Quote Link to comment Share on other sites More sharing options...
Challenger Posted May 31, 2009 Share Posted May 31, 2009 Stock downpipe? So would you expect similar gains by simply removing most of the exhaust and installing a glasspack? aka this.... I assume if its the stock dowpipe you basically made from the downpipe back? Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted May 31, 2009 Share Posted May 31, 2009 I had a set up like that challanger with the glasspack and with out the glasspack. The glass pack defenitly slowed my car down when i did it. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted May 31, 2009 Author Share Posted May 31, 2009 Stock downpipe? So would you expect similar gains by simply removing most of the exhaust and installing a glasspack? aka this.... I assume if its the stock dowpipe you basically made from the downpipe back? It would be near impossible to run a 3.5" downpipe and so I kept the stock downpipe. Mind you, Jon cleaned and ported the inside of the downpipe as it is a cast piece, paying attention to the area around the Oxygen sensor (using a die grinder). The stock downpipe is already 3" so a large diamenter. I do not like those Glass packs, Cherry Bombs, they are old '60 technology and I woiuld never recommend them. I had a set up like that challanger with the glasspack and with out the glasspack. The glass pack defenitly slowed my car down when i did it. +1 to Jeffer's statement. Yasin Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 31, 2009 Share Posted May 31, 2009 For reference, I made 260rwhp with the entirely stock ZXT fuel injection system BUT, I ran a Begi-RRFPR after the factory FPR, and a walbro pump. At 14psi boost, I was climbing to about 65psig fuel pressure. I didn't have a WBO2 sensor but on the dyno, I could get it to run too rich if I went over 65psi fuel pressure @14psi @5500rpm. The intake/exhaust/turbo were not stock. It's just a reference suggesting to you that the stock fuel injection should not be going lean at 185rwhp and can very well support more HP. Nice test. Impressive gains. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted May 31, 2009 Share Posted May 31, 2009 Check to see whether the vacuum line to the fuel pressure regulator actually applies vacuum/pressure to it. I had a car that did the exact same thing and found someone had pushed a ball bearing into the line to plug it. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted May 31, 2009 Share Posted May 31, 2009 I was surprised I picked 25whp (!!) and 11wtq (ft.lbs) Maybe peak, but that doesn't tell much of the story. Look at your curves again! You made almost 30rwhp from 4800rpm to redline, and 20rwhp at 3400rpm from a much quicker spoolup. Noticeable gains from 2800rpm to redline, serious area under the curve added on the HP side. On the torque side at 5200rpm and higher you picked up 25ft-lbs, no wonder you need more fuel!! Substantial gains from 2800rpm and up. Once again proving, a good exhaust system is the best bang for your buck on the Z turbo motors, and in general, most turbo motors. Quote Link to comment Share on other sites More sharing options...
slown280z Posted May 31, 2009 Share Posted May 31, 2009 The glass pack defenitly slowed my car down when i did it. It would be even worse on a turbo motor. It's all about exhaust velocity. The glasspacks have huge louvers that create turbulent airflow irregardless of which way you put it on. Good "resonators" (like Magnaflows and Dynaflows) not only do they use stainless packing that doesn't burn out, but they are not louvered, rather they have slats cut out into the packing so as to not impede airflow as much. The Bad News: I am still having a problem with the car in that it starts running lean from 4,500 to redline (look at my AFR curve), it goes from the mid 10s to mid 12s. I think that AFR curve actually looks pretty decent. I have seen others mention (most noteably Tony D) how much fuel you can pull and timing you can add past the torque peak on these motors. Also, 12.5:1 AFR is still pretty good for power making past torque peak. Quote Link to comment Share on other sites More sharing options...
aarang Posted May 31, 2009 Share Posted May 31, 2009 My '83 turbo ECU did the same thing.....leaned out after 4500 rpm. I don't think it is a fuel supply issue as much as an ECU control issue. I am now using an '82 ZXT auto ECU, as it doesn't seam to have the same problem. Funny thing, I have tried numerous ECU's from different years...the car runs differently with each one! Aaron Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted June 1, 2009 Share Posted June 1, 2009 Also check your grounds.. Check the AFM connection make sure everything is plugged in solid and clean connections.. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 1, 2009 Share Posted June 1, 2009 Maybe peak, but that doesn't tell much of the story. Look at your curves again! You made almost 30rwhp from 4800rpm to redline, and 20rwhp at 3400rpm from a much quicker spoolup. Noticeable gains from 2800rpm to redline, serious area under the curve added on the HP side. On the torque side at 5200rpm and higher you picked up 25ft-lbs, no wonder you need more fuel!! Substantial gains from 2800rpm and up. Once again proving, a good exhaust system is the best bang for your buck on the Z turbo motors, and in general, most turbo motors. Does this mean we should reference this point in the future when there are arguments about JeffP's dyno runs on his 3" system improving by 20HP? The next step is a flury of rationalizations about 'how' the HP was made... Good Information! Another chink in the armor of 'loosing your bottom end' argument when you add a big tube to an otherwise stock ZXT... And the revelation of the stock downpipe....WOAH! Surprising tidbit there! Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted June 1, 2009 Share Posted June 1, 2009 Is the stock downpipe really 3"? I didn't think so. As far as the AFR's past 5500 rpms, they do look acceptable. The stock turbo cam makes reduced power up there anyhow. You could shift around 5000rpms, be safe, and not lose anything. http://dcerutti.smugmug.com/photos/87171623_sLBj2-L.jpg Quote Link to comment Share on other sites More sharing options...
Challenger Posted June 1, 2009 Share Posted June 1, 2009 It would be even worse on a turbo motor. It's all about exhaust velocity. The glasspacks have huge louvers that create turbulent airflow irregardless of which way you put it on. Good "resonators" (like Magnaflows and Dynaflows) not only do they use stainless packing that doesn't burn out, but they are not louvered, rather they have slats cut out into the packing so as to not impede airflow as much. I think that AFR curve actually looks pretty decent. I have seen others mention (most noteably Tony D) how much fuel you can pull and timing you can add past the torque peak on these motors. Also, 12.5:1 AFR is still pretty good for power making past torque peak. Well I learn something every day... I guess itll be ok for now until I get it running right then Ill just strait pipe it. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 1, 2009 Share Posted June 1, 2009 (edited) TonyD, I have no idea what your getting at with your jeffp comment, can you elaborate a bit? I wish I still had a copy of the graphs, but here is a thread about the stock downpipe compared with a 2.5" mandrel bent one. http://forums.hybridz.org/showthread.php?t=108578&highlight=downpipe+stock Edited June 1, 2009 by Drax240z Quote Link to comment Share on other sites More sharing options...
slownrusty Posted June 1, 2009 Author Share Posted June 1, 2009 Is the stock downpipe really 3"? I didn't think so. As far as the AFR's past 5500 rpms, they do look acceptable. The stock turbo cam makes reduced power up there anyhow. You could shift around 5000rpms, be safe, and not lose anything. http://dcerutti.smugmug.com/photos/87171623_sLBj2-L.jpg Yes the stock downpipe is 3" I will take some pics and post it. Good point on shifting at 5k. Some interesting conversation here. Regards- Yasin Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted June 1, 2009 Share Posted June 1, 2009 This ties in well with the butt dyno when I went to a 3" exhaust and cat after putting in a T3/T4 on my '82ZXT. I did some runs at stock boost and then cranked it to 10PSI and both scenarios resulted in MUCH better pickup. Please don't take this as gospel, but the ECU goes into open loop mode under boost, and the maps that are programmed into the ECU are not right. I agree with others that too many people think that a low AFR is needed when boost goes up - especially after peak torque. I feel that 11 or 12 is the range starting from peak torque to max rpm - slowly declining as rpms rise. An aftermarket ECU that can control bigger injectors (for more boost) and ignition (to maximize off boost driveability and avoid detonation) is almost a necessity to my way of thinking - no more troubleshooting our state of the art factory system from 25+ years ago, and the wiring harness - rip the stock stuff out and really ENJOY our newfound driveability and power. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 2, 2009 Share Posted June 2, 2009 TonyD, I have no idea what your getting at with your jeffp comment, can you elaborate a bit? Some time ago there was a protracted debate over wether JeffP's 3" downpipe and exhaust 'really' added 20HP. It devolved into 'what really caused the increase in HP' some thinking the freer flowing exhaust made more boost, etc etc etc... Parsed and rationalized to death End result was Jeff simply claimed he put the exhaust on first, before changing anything else, in order to see what the HP increase would be. This is kind of a similar suituation, I was just waiting for the 'what really caused more horsepower, it can't just be the bolted-on exhaust' conversation to start! Quote Link to comment Share on other sites More sharing options...
johnc Posted June 2, 2009 Share Posted June 2, 2009 To determine where the horsepower came from we would need the motor insanity calculation sheet. Quote Link to comment Share on other sites More sharing options...
softopz Posted June 2, 2009 Share Posted June 2, 2009 No way a stock 280zxt downpipe is 3 inch because the outlet of the turbo is 2.5 ...its 2.5 cast iron with 2 90 degree bends. I think you can pick up another 5hp atleast with a new custom 3" dp. impressive gains though now turn up the booooost baby Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 2, 2009 Share Posted June 2, 2009 I think you can pick up another 5hp atleast with a new custom 3" dp. Check the link in my post about 4 up the list, I made a lot more than that with just a mandrel bent 2.5" DP swap. Quote Link to comment Share on other sites More sharing options...
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