John Scott Posted April 27, 2000 Share Posted April 27, 2000 For those of you who have had your engines dyno'd how much is the going rate. I'd like to put mine on a chassis dyno, since I'd rather not pull the engine. Are the coast down subtraction figures accurate for converting to flywheel hp? Also, since I'm playing with some high boost lately, how do you figure how much race gas (114 octane) to combine with premium (wimpy 91 due to our altitude) to acheive a desired level. 1:4 for 97, 1:1 for 103 ?? I know octane boosters are just band-aids, there's no substitute for good gas. Running more octane than you need, I've heard, will hurt perf. Still I don't want the insides of my engine saying howdy to me due to detonation. My effective comp. ratio with 7.5:1 @ 16 psi is around 13:1, the max allowed for pump gas. Intercooler will allow me a 16:1 effective c.r. safe on pump gas, but for now I need the safe gaurd of higher octane since I'm seeing 18psi w/o intercooler. What comp. ratios are you high compression racers running, what kind of gas? JS [This message has been edited by John Scott (edited April 27, 2000).] Quote Link to comment Share on other sites More sharing options...
MYRON Posted April 27, 2000 Share Posted April 27, 2000 John, I run pump gas in mine and have aprox 10.5-1 c.r. and the car runs great... I have a buddy that tried running race gas in his race car and it killed the performance because(he claimes) is because his motor is a low 11.0 compression... Quote Link to comment Share on other sites More sharing options...
Guest RON JONES Posted April 28, 2000 Share Posted April 28, 2000 John,I,m at 13.8:1 and I run VP C14 (114 octane).It runs great.I,ve been told that I could run C12(112 octane),but I,d rather be safe than sorry.On my smallblock that was supercharged,I ran It more on the street than at the track.Pump gas was all I ran in it for the most part.When I had it apart,there were some signs of detonation(only 10lbs. of boost).Becareful if your under boost alot,on pump gas you could hurt it.On your post I see 13:1,the max aloud for pump gas.From what I understand,if you try to get away with 11:1 on pump gas, your really pushing your luck. [This message has been edited by RON JONES (edited April 27, 2000).] Quote Link to comment Share on other sites More sharing options...
Mikelly Posted April 28, 2000 Share Posted April 28, 2000 11:1 was also what I was told when looking into putting a procharger on my truck. You can really hurt a motor once you get into anything above 10:5 to one on pump gas... The poor grade fuel we run here in the states doesn't fare well. Mike ------------------ "I will not be a spectator in the sport of life!" mjk Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted April 28, 2000 Share Posted April 28, 2000 Hi be careful with hi compression with pump gas. Remember 9.5:1,10.0:1 is the max, thats with a perfect tune car with iron cyl heads, remember iron cyl heads retain more heat, and you will need a big cam to bleed off some cylinder pressure at low engine speed, or go to a aluminum cyl head and go as high 11.5:1, because they disipate heat more quickly, keeping an eye on ignition timing, temperatures, carb tuning,also don't jump on the throttle in high gear. Quote Link to comment Share on other sites More sharing options...
John Scott Posted April 28, 2000 Author Share Posted April 28, 2000 I guess I should have given a little more info. The effective c.r. was given to me by Procharger as the max. allowable for THEIR system on pump gas with 7.5:1. 16 psi with 7.5:1 piston c.r. will give a "safe" effective ratio of 13.0. For example a 9.5:1 engine can only see 7 lbs. boost max. The lower the piston comp ratio the higher the effective. Thats why I went with the ultra low c.r. Intercooling is a much higher # for 7.5:1, 25+ psi ON PUMP GAS! Roots type blowers are well under these figures. I don't think ATI wants a bunch of lawsuits over their claims. At 16 psi, there is no detonation on premium fuel. I've pulled my engine apart on three different occassions while running the 14 psi, and other than when I was going through my tuning phase,(lots of abuse/ too much timing, lean jetting) everything looked great. Pistons/rings were fine, rod bearings showed a slight indication of detonation. Since then, I've got my tuning pretty well dialed in and I'm on 4+ years of pretty hard driving. Lately, with the boost change, and since I'm somewhat over their recommendations, I'm running 104 octane booster, until I can figure how much race gas/prem. to run. When I get it to the strip I don't want to be choking it down with over rich fuel. I know some people blend their fuel. Just trying to figure out how much to run to bump the octane #s a few notches. JS [This message has been edited by John Scott (edited April 27, 2000).] Quote Link to comment Share on other sites More sharing options...
John Scott Posted April 28, 2000 Author Share Posted April 28, 2000 Thanks everyone for the replies and suggestions, Drax, no intercooler yet, but I just got the dimensions (they're big!) and pricing info last week. As I said earlier, I'm at the edge now for pump gas and need a buffer. I think I'll follow Ron's suggestion or go with a 50/50 mix. I built my engine with the intentions of driving it hard. My builder spent a lot of time making sure it could take lots of abuse. I should have opted for the 4 bolt back then, but I was convinced that I'd never see more than 10 psi. I don't plan on always pushing this much boost, but as easy as it is to swap drives for race days, I need to be doing some experimenting, and if I don't push it, I'll never know what it is cabable of. I thought I'd be happy with 8 psi 5 years ago! I'll always want more! The intercooler is suppossed to add another 10% hp at a few lb lower psi. and will definitely give me all the room to 20+ to play with. I won't run over 18 until I get the 4 bolt upgrade, about a $500 machine/parts bill. By then I can re-ring/ bearing, and give the insides another good look. Now, has anyone gone to a Dynojet or similar facility? JS [This message has been edited by John Scott (edited April 28, 2000).] Quote Link to comment Share on other sites More sharing options...
Guest RON JONES Posted April 29, 2000 Share Posted April 29, 2000 Most tracks have a pretty good range of fuel to choose from,100 octane should be fine.This way you don,t have to go through all the mixing and you know what you have. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 29, 2000 Share Posted April 29, 2000 John, do you have an intercooler in the works? You haven't really mentioned it at all in your posts, except that you aren't running one. Seems to me you might be better off to spend the dough on an intercooler and run pump gas than to run race gas without an I/C... ------------- Drax240z L28TURBO transplant on the way! http://members.xoom.com/r_lewis/datsun.html [This message has been edited by Drax240z (edited April 28, 2000).] [This message has been edited by Drax240z (edited April 28, 2000).] Quote Link to comment Share on other sites More sharing options...
pparaska Posted April 30, 2000 Share Posted April 30, 2000 John, Drax, What intercooler are you going to use? The guys on Zcar.com (James Thagard, etc.) swear by the Isuzu NPR Truck intercooler. It's huge! I know my Eclipse GSX's intercooler is way small. 20 or 30 seconds of 15psi boost and it's quite warm. Oh well, I'll save that money for the Z . Quote Link to comment Share on other sites More sharing options...
John Scott Posted April 30, 2000 Author Share Posted April 30, 2000 Im going to use the ATI designed intercooler for the Procharger. They claim their two row will be more than enough for 4-500hp applications. They make a bigger 3 row, but claim it will be overkill. I think it is about as big as my radiator. About 24", 3" deep. When I get the clutter of my trans cooler out of the way it should fit pretty well. JS Quote Link to comment Share on other sites More sharing options...
Drax240z Posted April 30, 2000 Share Posted April 30, 2000 Well I am going to follow Scotties advice and not go cheap on the I/C... I'll probably try to find the NPR I/c and then once I fail at that I'll make a run down to Boeing Surplus and pick myself up a big aluminum heat exchanger and make one out of that. ------------------ Drax240z 1973 240z - L28TURBO transplant on the way! http://members.xoom.com/r_lewis/datsun.html Quote Link to comment Share on other sites More sharing options...
John Scott Posted April 30, 2000 Author Share Posted April 30, 2000 Drax, What is your definiton of cheap for an IC? Performance #s, $$. Just curious. They don't give the new ones away at ATI. JS [This message has been edited by John Scott (edited May 01, 2000).] Quote Link to comment Share on other sites More sharing options...
Drax240z Posted May 1, 2000 Share Posted May 1, 2000 I'm not really going on any personal knowledge here, just what I have heard from the turbo guru's that I've had contact with or read posts from. (mostly on zcar.com) Cheap = starion or supra I/C. Just big enough to get the job done on those engines, and not a whole lot of potential beyond that. I don't know flow numbers at all, but I doubt these ones would allow an L28T get beyond 275hp or so. Maybe not even that. ------------------ Drax240z 1973 240z - L28TURBO transplant on the way! http://members.xoom.com/r_lewis/datsun.html Quote Link to comment Share on other sites More sharing options...
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