Boosted_One Posted October 10, 2002 Report Share Posted October 10, 2002 Hi, The damage is consistent with pre-ignition or detonation. It likely melted under boost. can't melt on decel as the engine makes no power and the fuel cut under vacuum cuts off all fuel- no fuel-no combustion-no heat, The air coming in actually cools everything down super quick. Caused by too much boost, too lean, not high enough fuel octane, too much timing, plugs to hot on the heat range. If the fuel pressure holds under boost at high rpm and boost and duty cycle is less than 90%, the mechanicals are ok. 5/16 fuel line is fine to over 600hp. If it is programmed too lean, it will melt even JE pistons. Cheers, Ross ---------------------------------------------------- Mike K wrote: > Hi Ross I just had my car on the dyno. On the last pass I shattered a > JE forged piston: This happened when Iet off on the last pass on > decel, it didn't happen under load which confuses me. Is there any > way this was caused by having the map values shut off on high vacuum > readings? I have 0's on my MAP values above 24". This is a turbo > charged Starion 2.6L BTW. I run stock fuel lines and a high pressure > pump. Do you think a larger fuel line will be needed? Here is my > last dyno run: Thanks Mike K Link to comment Share on other sites More sharing options...
chiplee Posted October 10, 2002 Report Share Posted October 10, 2002 A little brief wasn't he? I'd want some more out of the guy myself I mean he didn't really even address all of your questions. Just told you that it was impossible for that to happen off boost. SDS provides good tech support right? I've heard they're great. Anyway, he has a firm grasp of the obvious if you ask me and pretty much just covered all the common possibilities. We'll get it figured out and know exactly what happened eventually Mike. I like what he said about the fuel lines though Link to comment Share on other sites More sharing options...
Boosted_One Posted October 10, 2002 Author Report Share Posted October 10, 2002 That how Ross is in email. When you call he'll talk your ear off. He answered my question though,about the decel and map values below the 24" range. Link to comment Share on other sites More sharing options...
Quest4Power Posted October 10, 2002 Report Share Posted October 10, 2002 which cylinder's piston went? was it #4? Link to comment Share on other sites More sharing options...
Boosted_One Posted October 10, 2002 Author Report Share Posted October 10, 2002 I've got 2 bad pistons. #4 is the cracked one #3 is mushroomed over in the same place where #4 cracked. Block is beyond boring due to the cracked piston in #4. Several large gouges that would be low spots if it were honed. It needs to be rebored. Link to comment Share on other sites More sharing options...
Quest4Power Posted October 10, 2002 Report Share Posted October 10, 2002 ok, i just read your other post. #4 it was. have you thought about a Dual Feed fuel rail? in most cars with large injectors the first three injectors will starve the #4 injector of fuel, causing it to run lean and detonate independently of what's going in in #1-3. this is a super common problem on turbo'd miatas and it always fixes the lean #4 problem. basically you add another fuel inlet on the end of the fuel rail that is the return side, then put a return in the center of the rail, then tee your fuel feed to both ends. you get much more even fuel volume that way with the big injectors that you run. Link to comment Share on other sites More sharing options...
Boosted_One Posted October 10, 2002 Author Report Share Posted October 10, 2002 That's a really great idea. But the fuel regulator is built into the rail at the end. Ulitmately that would mean I would need to relocate the regulator. Wouldn't a larger fuel line supply more volume to get around a starvation problem? How is it set up, got any pics from one of your Miata amigos? Link to comment Share on other sites More sharing options...
Quest4Power Posted October 10, 2002 Report Share Posted October 10, 2002 i'll find some... http://www.15psi.com/DSC00336.JPG this one's not for a miata but it's the idea that counts http://fast4s.net/ERDT/misc/reviews/visrail/IMG_6939.jpg Link to comment Share on other sites More sharing options...
chiplee Posted October 10, 2002 Report Share Posted October 10, 2002 umm isn't number 4 at the back? fuel enters the magna fuel rail at number 4. Following this logic number 1 would have failed in Mike's engine. Or am I missing something? Link to comment Share on other sites More sharing options...
Quest4Power Posted October 10, 2002 Report Share Posted October 10, 2002 umm isn't number 4 at the back? Â fuel enters the magna fuel rail at number 4. Â Following this logic number 1 would have failed in Mike's engine. Â Or am I missing something? good point, i hadn't noticed that before. Link to comment Share on other sites More sharing options...
Boosted_One Posted October 10, 2002 Author Report Share Posted October 10, 2002 At this point I am questioning a heck of alot. LOL! Link to comment Share on other sites More sharing options...
Shelby Posted October 10, 2002 Report Share Posted October 10, 2002 Mike i would n't question the experts but heres a little lesson learn'd running chyr big block 440's with two carder AVS's the stock carb's wouldn't hold more then 12lb of fuel pressure befor pushing the neddle and seat off causeing flooding, so with the two carbs the problem was solve'd by running 3/8 fuel line and not the 5/16 they came with , this alow'd us to use less fuel pressure, and still maintain engought fuel at 10 psi to keep both carbs full point being theres two ways of moveing fuel , volume and pressure , a larger line will always alow the same amount of fuel to be deliver'd at much less pressure then a smaller one will almost all inj's have an ideal fuel pressure working range where they can maintain a proper atomization of the fuel , too much or too little pressure up sets this pattern , even if as he says the 5/16 could flow enought to maintain the proper fuel volume, i can't see what haveing a larger fuel line could hurt, it would at the very least help keep the fuel pressure from haveing to be rasie'd too much , alowing the pulse width to do the mixture corecting as it should with out a sevier raise in fuel pressures , but i guess this will al be work'd out by next yr or hopefuly it will , trial and error gets real expensive huh Link to comment Share on other sites More sharing options...
Lizzord30 Posted October 11, 2002 Report Share Posted October 11, 2002 Just change your fuel lines whats the worst it can do? It doesnt coust much to do. I wouldnt blame SDS.... Link to comment Share on other sites More sharing options...
Boosted_One Posted October 11, 2002 Author Report Share Posted October 11, 2002 not blaming anyone. I'm posting info and trying to get some input, I'm not on a finger pointing mission. Link to comment Share on other sites More sharing options...
Shelby Posted October 11, 2002 Report Share Posted October 11, 2002 i ment that i wasn't trying to question the expert's ,not that i was one in any sence of the word , i'm just an old "wrench" here to learn like a lot of others a lot of very intersting stuff has come up in these last few threads Link to comment Share on other sites More sharing options...
Boosted_One Posted October 11, 2002 Author Report Share Posted October 11, 2002 Shelby Your info is invaluable. Someone said don't blame SDS and that's what I meant. You keep your knowledge coming Shelby! I for one am glad we got an old school muscle car guy. Link to comment Share on other sites More sharing options...
Joel Posted October 11, 2002 Report Share Posted October 11, 2002 Personally, as been said before, I think it was heat (no detonation)... I think you had to much timing into it for a 13:1 AFR... very hot. My buddies FC rx7 did the same thing at 13.5:1, heard no detonation... just heard the rotor go (apex seal broke)... Joel Link to comment Share on other sites More sharing options...
Lizzord30 Posted October 11, 2002 Report Share Posted October 11, 2002 I think one thing we need to relise is that it is not static compression its what the engine does under full boost that matters (and you should get fuel according). Link to comment Share on other sites More sharing options...
Darryl_Horn Posted October 12, 2002 Report Share Posted October 12, 2002 Hey Mike, Sorry to hear about your engine. I am a little confused. Which end of the fuel rail are you feeding the fuel into (cyl 1 or 4)? What boost level and octane fuel were you running when the piston came apart? You have me wonder about how close to the edge I am??? Ross might be right about the detonation thing. Remember the Magna flows much more air than a stock intake at 20 psi, so detonation will happen sooner at that boost level. I found that running anymore boost than 17lbs on Sunoco 94 octane gas gave me detonation with the Magna. If I tried richening up the fuelcurve or backing off the timing it would just take power away from my car, so I would think that 17 psi is optimum boost while running 94 octane fuel. I am presently mixing 100 octane Aviation fuel with pump gas inorder to run 20psi. Starting from the trunk my fuel system consists of a Bosch racing pump good for 500 HP, stock fuel lines to engine bay, a BG high flow fuel filter with a 3/8" ID fuel hose feeding the rear of fuel rail. I have the fuel rail inlet tapped to 1/4NPT and I am using a 1/4 NPT Stainless Steel 90 degree street elbow threaded into it. I am using 72 lb siemen injectors. I am also using the stock Magna fuel regulator with a uniasia boost referenced fuel regulator piggybacked in the return fuel line to bring the fuel pressure up to about 43 lbs at idle and 60 lbs while under boost. The Magna regulator won`t maintain a high enough fuel pressure by itself. Link to comment Share on other sites More sharing options...
Boosted_One Posted October 12, 2002 Author Report Share Posted October 12, 2002 Darryl I run the fuel inlet starting on #4. I was running 93 ethanol blend pump gas. The piston went at 18psi. I was having a little problem at 15psi but I got that under control. At 18psi it was out of control. I dialed in a lot of fuel and, was at 255 on my map readings at 18psi!! I couldn't get anything more than 15psi to run decent on pump gas. Fuel pressure is 34 baseline, 1:1 with my fuel pressure reading ~50 at 15 psi with 75lb injectors. I used the stock FPR as it always held the pressure consistent. SDS told me as long as the fuel pressure is holding and your not maxing out your duty cycle your alright. Your doing it right Darryl. Kept that high octane fuel in it! I would love to see your car on the dyno Darryl. Link to comment Share on other sites More sharing options...
Darryl_Horn Posted October 12, 2002 Report Share Posted October 12, 2002 With the fuel pressure at only 50 psi under boost you might be taking the injectors past there duty cycle? Before I piggybacked my regulator on the Magna I had to run a higher fuel curve number on the SDS then when I was using the TEP intake with the 52 lb injectors. Link to comment Share on other sites More sharing options...
Quest4Power Posted October 12, 2002 Report Share Posted October 12, 2002 yeah, it seems you fuel pressure was pretty low at that high of a boost level. should be more like 40psi baseline and 1:1 rate of rise per psi for those big injectors and the 20G. darryl did make a very good point there, i hadn't paid much attention to your pressure numbers. i ran those numbers by a local dyno tuner and he said your working pressures look a bit too low for that size injector/turbo combo. Link to comment Share on other sites More sharing options...
Shelby Posted October 12, 2002 Report Share Posted October 12, 2002 just as a referance the last dsm 91 lazer i ran a fuel system check on the stock reg they use was 46lb at idle and 56lb at 10lb of boost , the dsm reg looks like it may fit the aussie fuel rail with a mod to the bolt down bracket , not sure if that would help or not , but the fuel reg will give more then 56 lb, not sure ho much more tho Link to comment Share on other sites More sharing options...
Tim_C. Posted October 14, 2002 Report Share Posted October 14, 2002 Maybe your volume is such that you need 8 smaller injectors with a higher baseline for optimal atomization? Or, run 45-50+ PSI baseline on the 4 bigger injectors to see what that does for duty cycle to volume ratio? I really like the bigger fuel line idea. But, a higher baseline pressure will atomize better, so when you increase the fuel, it will still spray well enough to give HP, not lose it like what is happening to Daryl? I think Daryl's point of detonation at 17 PSI could be due to a loss of atomization characteristics. My engine just loves high fuel pressure. Even before, it really ran better, and even boosted 1PSI or so more when I turned up the baseline pressure to 50. Of course, now my baseline needs to be 70! Needless to say, it is parked until I get the fuel somehow. That's why I'm watching all these threads, and maybe being a little pesimistic at times. I'm about ready to go one route or another, and need to decide. I'm leaning toward an added injector since I can actually get there @10PSI boost with what I have. Just some thoughts. Tim C. Link to comment Share on other sites More sharing options...
TurboRaider Posted October 14, 2002 Report Share Posted October 14, 2002 http://www.sacskyranch.com/deton.htm Good pics and info o what detonation looks like.... In this case jet fuel got into the gas lowering the octane and damaging engines. Regardless of the cause the damage pattern is the same. Kevin C Link to comment Share on other sites More sharing options...
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