ZR8ED Posted October 17, 2001 Share Posted October 17, 2001 Hi folks.. is that a silly question or not? Well I was playing with the boost controler, and temporarily unhooked it (huge big story to this action...too long to explain) I took the car out for a blast. I use Sunoco 94 fuel, and I add 1 bottle of 104 octane boost... NO I/C installed yet. stock Z31 motor. I took it out, and the car ran to 15lbs..(what I modified my stock popoff valve to).. that was the test.... Anyways, the car ran perfect..no pinging..nothing but pure acceleration.. So here is the question..did my knock sensor do its job and turn back the ign timing??? I have heard that you can't run a Z31 turbo motor that high with out an I/C... or any turbo motor for that matter. I ran it on the highway, and did a 4th gear and 5th gear blast, and the motor sounded perfect..went like hell to!!! Now don't worry, I have it turned back now...I was just curious..the heat that is generated at that boost would nulify any serious hp increases (law of diminishing returns) is that correct? I'm just trying to get an understading why my motor did not blow up? BTW I have a greatly increased cooling setup with this conversion, and I didn't notice the temps climbing up very much when I did these tests. BTW 2 I have an I/C on the way..hehehe I want more boost!! Thanks, Scott. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted October 17, 2001 Share Posted October 17, 2001 Scott, If you really want to tell how it is running at those boost levels, do a 4th gear to redline and shut it off immediately..pull over on the side of the highway or whatever, and pull the plugs. Plugs tell everything about the engine. I have "heard" of people running up to 12 psi on a stock zxt engine, but most people recommend against it. I dont know how, sometimes mine knocks at 8 psi in 3rd+ at high rpms. Have fun and stay away from the popo! Scott Quote Link to comment Share on other sites More sharing options...
scottyMIz Posted October 17, 2001 Share Posted October 17, 2001 I had mine to 10 psi w/o an ic but i wouldn't do it again.Chances are the engine retarded it's self to reduce the detonation.I haven't touched my timing at all on my l28et.Either the ic is that efficent or the computer does a good job adjusting the timing.It depends on alot of things the gas, air temp,ect. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted October 18, 2001 Author Share Posted October 18, 2001 Thanks Scott and Scott. I have mine turned back to about 11 lbs right now. I am assuming the additional octane, greatly increased cooling, and i'm starting to think the lighter weight of the car is allowing me to run the extra boost with no ill effects...and these days the temps are dropping quite a bit also. It was incredible how fast the boost went from vac to full boost when I would floor it! the engine doesn't sound like it is working very hard..and I proved it when I had the 4.11 diff in there..the 3.7 also.. I could not reach max boost in the lower gears 1-3 the 3.54 diff made all the difference in the world....it was strange to see the car get faster as I decreased the ratio..If I had a 3.36 R200 I would have tried it too!! hehehe The motor really likes to be under load. I figured that nissan engineered the motor that way..it did after all have to lug a 300zx 2+2 around...we are talking almost 800lbs difference in weight between the donor car and my 280Z. Now if I can only get that power to the road off the line I'll be all set. Thanks, Scott. Quote Link to comment Share on other sites More sharing options...
260DET Posted October 18, 2001 Share Posted October 18, 2001 An intercooler reduces the thermal load on the engine and increases engine efficiency by helping the delivery of more air (oxygen) to it. Both as a result of delivering cooler air. Don't know specifically about the Z31 engine, but others can run 15psi boost without an intercooler. But, as a rule of thumb, around 15 psi is the limit as far as efficiency and engine safety are concerned. Depends a lot on the engine design, ambient temperature, fuel, engine management system efficiency, etc. The best part about running high boost is that kick you get when the turbo spools up from zero to big boost in a split second Quote Link to comment Share on other sites More sharing options...
Guest MegaShaft_2000 Posted October 23, 2001 Share Posted October 23, 2001 quote: Originally posted by Z_Ferrari: Scott, If you really want to tell how it is running at those boost levels, do a 4th gear to redline and shut it off immediately..Scott I don't think that's too good for the turbo to run it hard and shut the engine off. The oil may coke in the turbo, and could result in a clogged up lubrication system. That's why many turbo car drivers use turbo timers, to idle the engine for a while to cool off the turbo. Quote Link to comment Share on other sites More sharing options...
GrayZee Posted October 25, 2001 Share Posted October 25, 2001 "It was incredible how fast the boost went from vac to full boost when I would floor it! the engine doesn't sound like it is working very hard..and I proved it when I had the 4.11 diff in there..the 3.7 also.. I could not reach max boost in the lower gears 1-3 the 3.54 diff made all the difference in the world....it was strange to see the car get faster as I decreased the ratio..If I had a 3.36 R200 I would have tried it too!! hehehe The motor really likes to be under load." Thank you for confirming that ZR8ED.. I asked a similar question but I don't believe anyone answered me. I was thinking of putting a 4.11 in my 76zt but I guess I'll stick with the 3.54! The more load you put on the engine the more the turbo likes it! [ October 25, 2001: Message edited by: GrayZee ] Quote Link to comment Share on other sites More sharing options...
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