Scottie-GNZ Posted May 12, 2001 Share Posted May 12, 2001 My buddy and I finally got around to doing some serious testing to find the source of my problem. We hooked up a FP gauge with a long hose that extended into the car next to the boost gauge. We also put temp probes at the compressor outlet and the TB inlet. Was hoping to have a 2nd boost gauge connected at the compressor but could not come up with one. It was cloudy with an ambient of 73*. I was driving holding the FP gauge next to the boost gauge and he was monitoring the temp gauge, the datalogger and making notes . First test was to confirm that I had the required fuel pressure at high boost and saw 60# FP at 20# boost with a base of 40.5# at idle, vacuum off. No problem there. Immediately noticed that the temps were extremely high, 300+* at the compressor and 95-100+* at the TB. This was from a short 3rd gear burst and holding 20# for a few seconds. Not good. As a side note, I was using 215/60-15 Firehawk tires and had to ease into the boost in 3rd and with my relief valve setup that just was not possible. Even trying to ease it into it, when the relief valve opened at 15# (about 50mph), it would light up the tires and put the car sideways We then moved the boost gauge to the compressor, eased into the throttle and WHAM, 27# boost. WTF!!! Tried it again, 30# boost . Conclusion: I have a massive leak somewhere between the compressor and the TB. I suspect the I/C has a decent size crack at a seam or is badly clogged. Could also be a hose as I have heard of silicone hoses having splits that were hard to see but opened up under boost. Will be a couple of days before I pull things apart and test the I/C, but I am as happy as a pig in you-know-what. Strange how bad news can make you happy. This all now makes sense as to how you could have knock despite not running lean. At the track, with the burnout, spooling up at the line and running full boost for 11-secs, I cannot imagine what the temp must have been at the TB. I would guess 50-75* above ambient. Hopefully it is something as simple as a split hose but if it is the I/C, it should be repairable. Lets get this puppy repaired and see what it will do with 24# boost. Quote Link to comment Share on other sites More sharing options...
TimZ Posted May 12, 2001 Share Posted May 12, 2001 Sounds like you are on to something there. From your description, I doubt that your problem is a leak, though. I'm more inclined to think that you have a restriction somewhere between the compressor and the TB. Maybe a restriction, followed by a leak. The most obvious culprit is the intercooler. I'm not sure how to flow test one of those, but it would be interesting to see what pressure drop it generates for a given amount of airflow (specifically, the amont of airflow you generate at 20lb of boost). As I recall, your I/C was from a turbo diesel application. I'm guessing that you are flowing quite a bit more through it than it's designers intended. Another possibility, depending on how you have your crankcase vented, is that the intercooler is filling up with blowby oil, which is actually pretty common in turbocharged engines. This would cut off the bottom tubes of the I/C, and effectively make the intercooler smaller and smaller as it fills. Also, any oil spray lining the walls of the remaining tubes will greatly reduce their efficiency, and if any of it gets to the intake, it will reduce the effective octane of your fuel. Anyway, that's where I'd start looking. Good job in using instrumentation to identify your problem areas, BTW. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted May 12, 2001 Share Posted May 12, 2001 Way to go Scottie! I hope the fix isn't going to be too expensive for you. It's kinda like, "yeah, I found out that both my aluminum heads I bought are cracked, that would explain the problem." It pains me to hear stuff like that...all the $$$($!). All the best, David Quote Link to comment Share on other sites More sharing options...
stony Posted May 13, 2001 Share Posted May 13, 2001 Scottie. i agree with TimZ Alot of guys in japan would use stock gtr intercoolers for crz's and small 4 bangers and would work well but they still dont flow as well as a good aftermarket intercooler. If you do not find any leaks i would invest in a good spearco youd be amazed at the improvment. turbine spools up alot faster low end torque improves also. I think sticking with a npr or other stock intercooler is a good budget idea but not when youve got alot invested into a project. a good intercooler can really liven a motor up. my 2 cents stony Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 13, 2001 Author Share Posted May 13, 2001 Tim, you make excellent points. I plan to cap the I/C pipes, with one cap having a small hole for my air gun. I will then submerge it and pressurize it. It probably will not be air tight but it is not so much a pressure test as it is a leak test. Last visual inspection of the I/C showed nothing that would indicate such a leak. Just got back from Home Depot and $2 got me 1' of 2" sch40 PVC and 2 2" caps. The PVC has an od of 2 3/8" and with a little duct tape it will fit snugly into the silicone hose. A light bulb just went off and I have a another and more likely culprit to check, the relief valve. I am measuring boost at the compressor and before the relief valve, but the relief valve is in the boost signal line for the wastegate cannister. If the relief valve is leaking, it would also act like a bleed-off valve or more likely, it is opening at 15# but not letting enough pressure through to the cannister to overcome the shortened rod which is preloading the spring. Puck stays shut. This model NPR is proven in the import drag world. There is a local turbo-rotary Corolla that runs mid-8s @ 157+ using this I/C. His car is light and he is spraying but I still put him at 600RWHP. These guys are not going to use it if does not do the job. I do not know what the pressure drop for this I/C is (rumored at 1.5#) but if the leak/restriction was not there you can assume the boost at the compresor would be more like 22# and the temp would be substantiallly less. If we get conservative and say 30* less, you can also assume the temp at the TB would be ambient or slightly over. Cannot ask for better than that at these boost levels with an air-air I/C. Not to worry, an upgrade is in the works. [ May 12, 2001: Message edited by: Scottie-GNZ ] Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted May 14, 2001 Share Posted May 14, 2001 TimZ's idea of oil in the intercooler is a good one, I've seen this. However pulling the TB hose and looking inside will reveal this problem real quick - it'll have oil all over it in there. My Mustang pushed oil past the turbo seals and made a mess, cleaning it out is a PITA! Pressurizing the intercooler and checking for bubbles is a good idea - wonder where you got that from (lol). I'd use very low pressure, be careful with a compressor. I don't think you'd want to cause a problem by giving it too much pressure (ahem). I'm going to be real curious to see what you find, sounds like the dumb as rocks knock sensor wasn't to blame after all! Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted May 14, 2001 Share Posted May 14, 2001 Hey Scottie, maybe that intercooler just sucks! Just kidding. I hope you don't find crankcase ventilation problems or some type of annoying restriction. I think that you will find it to be a severe pressure drop caused by the excessive flow you are trying to achieve with that turbo @20+psi of boost. By the way, TIMZ I know now why that restriction would kill performance even though intake temps are cool. You run outside the compressor effeciency on the map by having to produce 7 more psi of boost at the compressor to see the desired boost at the TB. IE, this could take you from an ideal 75% compressor effeciency to 50% compressor effeciency on the maps. That is why a low pressure drop intercooler is better regardless of intake temps being low. By the way Scottie, your new intercooler has been removed and will be modded by Tuesday and shipped for your driving pleasure. I see a 10sec 1/4 in your near future! Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 14, 2001 Author Share Posted May 14, 2001 I pulled the I/C and had a cursory glance. No oil (thats good) and no obvious leaks that could cause such a drop and thats also good . That means I can still give it to the person who's $$$ is burning a hole in their pocket. Ironically, an I/C swap was already in the works even before this discovery and it is now known that I am getting 240Z Turbo's UNDERSIZED I/C. If the NPR has no leaks when I test it, then the Z gods (you now who you are) were right and this beast is flowing more air than the NPR can move efficiently. So, whats your guess on how much HP this thing is costing me? 50? Come on, make me feel good. Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted May 14, 2001 Share Posted May 14, 2001 How much power you have lost due to excessive pressure drop is really hard to say. What compressor wheel are you running? From this you can look on the map and compare the compressor efficiency at 2.91(28psi) and 2.36(20psi). I am sure you will find you have run out of any desirable effeciency range and probably close to the surge limit of the compressor wheel. I was just looking at the maps on the Turbonetics homepage: http://www.turboneticsinc.com/comp_maps/fig9.html and from the looks of most maps the extra 7psi generated will really kill the power because of compressor efficiency. Therefore I conclude you will gain 300hp from using my intercooler! Feel Better? Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 14, 2001 Author Share Posted May 14, 2001 300hp!!! I will take it even though it is probably not enough to kick your butt Quote Link to comment Share on other sites More sharing options...
TimZ Posted May 14, 2001 Share Posted May 14, 2001 quote: Originally posted by Scottie-GNZ: 300hp!!! I will take it even though it is probably not enough to kick your butt Not enough? What - were you starting with 10? Quote Link to comment Share on other sites More sharing options...
TimZ Posted May 14, 2001 Share Posted May 14, 2001 quote: Originally posted by TimZ: Not enough? What - were you starting with 10? (Sorry James - couldn't resist...) [ May 14, 2001: Message edited by: TimZ ] Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted May 15, 2001 Share Posted May 15, 2001 He was starting with 9.8 to be exact! Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted May 15, 2001 Author Share Posted May 15, 2001 Hey TimZ, now that is funny but I better not laugh since I am now at his mercy. James, just remember it was not me that said that. . . . . snicker. [ May 14, 2001: Message edited by: Scottie-GNZ ] Quote Link to comment Share on other sites More sharing options...
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