Gollum Posted November 3, 2012 Share Posted November 3, 2012 In some ways it applies to both motors in question though. But really pharaoh, the way some of your statements are worded can be quite misleading. There's pushrod V8 drag cars running 13:1 compression ratio running 20+psi on ethanol.... Compression doesn't limit boost, it limits timing. Timing CAN limit power, but you have to understand the whole picture to figure out how much power you're "losing" from added compression. Just throwing a turbo on a NA engine without ANY other supporting mods probably WILL break some parts, but that has NOTHING to do with the turbo, but EVERYTHING to do with the tune. And you don't EVER lean an AF ratio because of compression. If you're trying to play it safe and keep the detonation at bay you enRICH your AF ratios. Adding excess fuel does a few things to reduce chance of knock. 1. Causes a slower total burn that can often push back the timing of peak pressure of combustion, 2. Cools the air charge as there's more fuel to be atomized, and in doing so transfers more heat from the chamber. 3. Causes the mixture to be harder to ignite (goes hand in hand with #1). When you start to look at the WHOLE picture you see that timing and mixtures are a dynamic duo. You can't change one without affecting the other. The leaner you run, the less timing you NEED to run for peak power (not CAN run before peak power, there's a difference, think about it). The richer you run, the more timing you CAN run, or CAN get away with as some people tend to tune. Most people get knock, so the add fuel in that area. That's ONE way to fix it. You could also pull timing in JUST that spot and see what happens. Oh, and personally..... If I were running a turbo on a P79 w/flat tops combo (read, quench heads, not open chamber) I'd run as THIN of a head gasket I could, PERIOD. That would REDUCE my chances of detonation, because though I might be adding a .1-.2 compression over factory, for that marginal increase I get much improved quench, and the more you can improve quench the better. The "perfect" setup for huge boost would be to run a MN47 with a dish piston that matched the shape of the MN47 chamber, to keep the quench areas flat against the piston, and keep the chamber spherically pancaked, hopefully landing you around 8:1 compression. That'd be "ideal" for someone wanting to run anything from pump gas to race gas. I personally want to build a MN47/flat top combo as a turbo motor for E85... And probably run 15+psi... And on a stock bottom end. Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 3, 2012 Share Posted November 3, 2012 Gollum, we are on the same page for sure, Brother! Quote Link to comment Share on other sites More sharing options...
bthomp Posted November 4, 2012 Author Share Posted November 4, 2012 So I take it your running the stock transmission then Tony? Lol I'm not an expert, nor have I started any auto mechanical engineering classes yet, but the differences in the t and NA block for cr are only slightly off from each other in the case that 8:2?, is still fairly low and not anywhere close to the 10 that giving the engine flattops give it.. in fact, as far as block goes, the head is where the real difference is for cr. Might be wrong about this though, been working triple shifts at work along with schooling the past 3 days so my brain is pretty fried right now. But if I am, sure you guys will correct me, or just pretend this section of the post never happened. I supported my turbo and tuned carefully until greed hit me and I stop paying attention to the engine... The car made it down to FL and back to MD, hell I lived down in Florida for 3 months and was using the car as a DD and made long trips down in FL...Just saying. I'm sure iv said this before and sure others will agree that this is probably the case... Detonation Did Not Cause My Piston To Melt!!!! Detonation=something went boom Melting piston=something wasn't cooling that cylinder, at all... On a side note to my original thread before this gets moved and changes into something else... Right now I think I'm going to test my VG swap and see how I like it. If I like how the car feels with the better center of gravity that much, then ill build it up. If not, go back to the L28, slightly modify the externals a bit more for a more reliable setup, bore the block so its useable again, and so on Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 4, 2012 Share Posted November 4, 2012 (edited) At the time it was stock, but the KA24 boxes are now my preference. A melted piston may be detonation. Preignition is another term to look up, and the interaction between the two. Detonation can break things, but it can also set up conditions were in audible precognition goes undetected and things just fry! My problem with Corky's book was it was outdated the second it was printed. The Watson text theorised a shift in terminology from the 70's scenario of boost threshold being where it made anything at all, and the newest (1982 engineering) that shifted the point to "full" boost as most wheel cuts were then to a point that "some" boost was available at ANY rpm. It made the historic paradigm of the 1960's Chevrolet Corvair style boost (none in first, nothing until near redline in second, get it strong above 3,000 in third...) unusable in the modern manufacturing context. Like the Hugh Macinness "Turbochargers" book, it was chock full of 60's information about overboard boost upping, and crap like that, to Corky's which was 10 years newer, but still using decade-old plus paradigms. Contemporaneously, Bob Tomlinson's book "Turbomania" is relatively unknown outside the VW world, but really addresses the proper application of multiple carburettor end turbocharged engines. But to have such puffery associated with Maximum Boost as "The Definitive Book on Turbocharging"? HOGWASH! I paid the $184 and was blown away by Watson's book, and it opened my eyes to the marketing and sales job that was being done in "Maximum Boost"... It was revised in 2003, second edition. I'd be interested in seeing the changes. I see its on torrents and as a PDF on some forums... Reading the first few comments on the book on Amazon currently, I see others see some of this as well. It's a nice primer, but it's hardly definitive, and definitely a marketing pamphlet! If ANY engineer could see the performance of a GT35R with a 0.63 Hotside A/R on an L28, they too would agree the definition of the turbo world to that point was useless. It makes 3psi off-idle, and with electronic controls now it's possible to get a boosted IDLE if you o desire! (Not great or housing and wheel longevity...) basically off idle giving it WOT and you to 3psi. So what relevance does the old definition of "Boost Threshold" have when in most any turbo today properly sized and installed, it effectively is "Zero"? Edited November 4, 2012 by Tony D Quote Link to comment Share on other sites More sharing options...
bthomp Posted November 4, 2012 Author Share Posted November 4, 2012 I have a feeling it was more towards the side of not cooling off, around that time my afr started to bounce a bit. Also when we took the injectors off the rail, that injectors was full of crap that you could see on the filter screen on top. We also too a look at the piston rings to see what they could tell us. It was kinda melted to the piston at the spot where the piston melted. But I shall not dismiss the idea of detonation and look more into it. I look around and see what I can find out about getting the 2003 version of the book and give it a read. At what point did you decide to switch up to the ka? Been wondering how much longer my stock will hold up and need to upgrade/replace it. Not a whole lot of info that I can find anyways about the stock trans. Quote Link to comment Share on other sites More sharing options...
Leon Posted November 5, 2012 Share Posted November 5, 2012 Just throwing a turbo on a NA engine without ANY other supporting mods probably WILL break some parts, but that has NOTHING to do with the turbo, but EVERYTHING to do with the tune. And you don't EVER lean an AF ratio because of compression. If you're trying to play it safe and keep the detonation at bay you enRICH your AF ratios. Adding excess fuel does a few things to reduce chance of knock. 1. Causes a slower total burn that can often push back the timing of peak pressure of combustion, 2. Cools the air charge as there's more fuel to be atomized, and in doing so transfers more heat from the chamber. 3. Causes the mixture to be harder to ignite (goes hand in hand with #1). When you start to look at the WHOLE picture you see that timing and mixtures are a dynamic duo. You can't change one without affecting the other. The leaner you run, the less timing you NEED to run for peak power (not CAN run before peak power, there's a difference, think about it). The richer you run, the more timing you CAN run, or CAN get away with as some people tend to tune. Most people get knock, so the add fuel in that area. That's ONE way to fix it. You could also pull timing in JUST that spot and see what happens. Nathan, you've flipped a few things here. A richer mixture burns faster and is easier to light off (makes sense when you think about it) than a leaner mix. Thus, leaner running requires more timing advance, and a richer mixture needs less timing to hit MBT (max brake torque). Quote Link to comment Share on other sites More sharing options...
Gollum Posted November 5, 2012 Share Posted November 5, 2012 Nathan, you've flipped a few things here. A richer mixture burns faster and is easier to light off (makes sense when you think about it) than a leaner mix. Thus, leaner running requires more timing advance, and a richer mixture needs less timing to hit MBT (max brake torque). Ah, you're right. I'm sorry. That said, you never lean out a fuel mixture to fix a detonation issue. Bad juju! Quote Link to comment Share on other sites More sharing options...
Leon Posted November 5, 2012 Share Posted November 5, 2012 Ah, you're right. I'm sorry. That said, you never lean out a fuel mixture to fix a detonation issue. Bad juju! That, I'll agree with! Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted November 6, 2012 Share Posted November 6, 2012 I wouldn't do the VG swap over again. A lot of effort for something marginally better. I'm swapping in a VG33 in whenever I decided to actually reacquire my car. After that.... VQ or 2JZ. new Ford 5.0L.... well, actually, turbo LSx is what I'm thinking. As much as I'd hate to give GM any support. NA LS Zs are everywhere. I can add the turbo(s) for a little more flair. Quote Link to comment Share on other sites More sharing options...
bthomp Posted November 6, 2012 Author Share Posted November 6, 2012 If I wasn't on an out of state college budget... I could see me doing something like an LS or 2jz swap... Just trying to work with what I have. Quote Link to comment Share on other sites More sharing options...
78zstyle Posted November 6, 2012 Share Posted November 6, 2012 I wouldn't do the VG swap over again. A lot of effort for something marginally better. I'm swapping in a VG33 in whenever I decided to actually reacquire my car. After that.... VQ or 2JZ. new Ford 5.0L.... well, actually, turbo LSx is what I'm thinking. As much as I'd hate to give GM any support. NA LS Zs are everywhere. I can add the turbo(s) for a little more flair. Do a turbo lsx. so little cost for so much power and reliability. Would be nice to walk all over pretty much any production car out there. Quote Link to comment Share on other sites More sharing options...
BLOZ UP Posted November 6, 2012 Share Posted November 6, 2012 If I wasn't on an out of state college budget... I could see me doing something like an LS or 2jz swap... Just trying to work with what I have. It gets more expensive. I've dumped 2-3 thousand on my swap. Keep in mind, I picked up the motor and an R200 for $500, the driveshaft was free, MS2 was free, the rest is the manifolds (about 700 all welded up), and the little things. Quote Link to comment Share on other sites More sharing options...
Gollum Posted November 6, 2012 Share Posted November 6, 2012 It gets more expensive. I've dumped 2-3 thousand on my swap. Keep in mind, I picked up the motor and an R200 for $500, the driveshaft was free, MS2 was free, the rest is the manifolds (about 700 all welded up), and the little things. Yes, if cost is a concern, the L28ET starts to look really good. No fabrication required. Saves a lot of time, energy, and overall hassle. Even if you have a welder handy, any swap starts to have added cost when it's a motor that never came in that chassis. Now, I've never felt that should be a huge reason to stop someone from doing a swap, but it certainly should be a factor in ANY budget. Quote Link to comment Share on other sites More sharing options...
bthomp Posted November 7, 2012 Author Share Posted November 7, 2012 Well I'm in the middle of putting my na vg in the 280 just so I can run the car for the moment. But yeah, the external side is basically all done for doing the l28. After all I DID have it turbod. And my ms is set up for it as well Quote Link to comment Share on other sites More sharing options...
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