you could go into it...

it would be interesting to learn...only downside for me is that there is only 4 stations in MD and if i go back to VA there is none

 

^^Yes! Please do Dave!! You know so much about this subject, it would be great to get as much first hand comments on this as possible! My biggest question is are the fuel tanks on the GK and RD tibs made the same way? I know you said that you have had no problems with your fuel tank. I just need to verify that mine will work. (sorry to temp. highjack this thread!) Also, Enthalpy (damon) is helping a guy tune and E85 MR2 I believe, and they are having some kind of aluminum oxide residue showing up in the intake manifold that they are concerned with getting into the combustion chamber. Had any problems with this??? I hated chemistry in high school! So, back to the point of telling us why we need more fuel and how it burns/reacts would be great man! : )

 

A Beta can have a full millimeter whacked off the bottom of the cylinder head. I have read at least two accounts of this being done. I wouldn't hesitate to take off 0.5mm, but then I'm also going to be making good use of clay to measure the valve/piston clearance when *I* finally get the $ for my engine build.

Of course it raises compression that is one of the OP's goals. The amount that it changes the timing is negligible (I made a thread on that very topic, and Red did the maths for us)

Stock pistons ARE strong enough for a lot of power IF the tune is spot-on. Bal broke some (I think forged) pistons under boost, with detonation from a bad tune. Singh grooves were part of his cure for the detonation. The other part was finally getting his tune dialed in. IheartmyRD (I think was him?) ran a higher compression ratio on 87oct. pump gas with singh grooves.

 

Ok, you asked for it! lol

E85 (Ethanol) has a much lower energy content than gasoline so it takes more E85 to maintain a lambda of 1 or stoich air fuel ratio promoting combustion. Gasoline stoich or lambda of 1 is 14.7:1 and E85 is ~9.6:1, see the difference? Now here's the cool part. The majority of the post '96 ECUs out there tune based on lambda value. The AFR value is just a calculation against the lambda value taking fuel type into consideration. So...from the above information you can state 14.7:1 (gasoline) = lambda 1 = 9.6:1 (Ethanol).

Follow me so far? So if an ECU tunes for lambda, NOT AFR then the ECU doesn't really car what fuel you put in your engine as long as it has enough injector to maintain its required lambda values. I tested this theory out on my GK tiburon with the wastegate arm disconnected so I didn't go into boost. All I did was some rough calculations as to what size injector I'd need to supply approx 30% more fuel. The stock GK comes with 190cc injectors stock, so 190 x .30 + 190 = 247cc injectors. They don't make drop in 247cc injectors so I had to go with 290cc injectors from a 2.4L Sonata. I dropped in those injectors after my tank was near empty and promptly filled up with E85 and reset the ECU. Car fired right up no problem! So I continued watching my fuel trims to see what the stock ECU was doing. Guess what? It trimed out the extra fuel and that car ran perfectly!
I monitored my fuel trims for the next week or so and they settled in at about +/- 7 for the short terms. Perfectly acceptable range! Another cool thing is that since most widebands use calculations based off of lambda value I can still use it to tune E85. smile.gif So for example my wideband displays between 14.5-15.1 AFR at idle and cruising. Now I know from the above equation that this is hovering around a lambda of 1 which equals Ethanols 9.6:1 stoich ratio. Perfecto! I can also use the wideband to tune the areas where I want richer AFRs as well since its all based off the univeral lambda values! So say I want around 12.5:1 gasoline AFR at WOT. I would shoot for the same value while running E85!
Now it gets a little trickier when running forced induction but all the same concepts apply. The added octane benefit of E85 (106) means you can actually advance ignition timing under boost to help cool combustion temps and actually help the turbo spool sooner. E85 runs a lot cleaner than gasoline so you also get a lot less carbon build up.
As for the RD fuel tank, what is it made out of? The GK one is steel so its got no problems with E85. I have yet to see any sort of weird build up anywhere in my intake or fuel systems. If you have issues a good fuel filter should cure anything getting into the fuel system.

 

That's pretty neat. Carburettors have their points . . . and computers obviously have theirs.

 

yeah, I've been extremely pleased with E85 thus far. Plus with my Perfect Power TF10 I'm adding in 6 degrees of timing under boost and the engine just LOVES it. Milage hasn't dropped to far from when my car was on gasoline. I average between 26-29 MPG Highway. Also I've got the TF10 rigged to a switch so if I have to put premium in it I can just toggle to my old premium map. smile.gif

 

@dddude55: tuning a car conservatively to avoid minor detonations and whatnot is not proper to me. yes, at certain situations it can be satisfactory. but satisfactory isn't proper. not to mention sometimes dangerous, but that's another story.

from my experience, E85 demands roughly twice the fuel as compared to regular 93 octane pump gas on the same vacuum/pressure level. it's good for prevention and power. price is quite cheap also (of course as compared to those C16s). I wouldn't recommend it though when only far away gas stations offer them. I heard some people having problems though on their fuel seals on injectors and whatnot. I had one in a customer's car, though it was my fault as the o-ring wasn't seated properly.

 

Like I stated, at least on my car, it needed about 30% more fuel to reach a lambda of 1, not 50%. I've had zero issues with o-ring or pump failure on my car and I've been running E85 for almost 3 years. smile.gif Plus I definitely like paying less than 2$/gallon as opposed to near 3 for premium.

 

Actually, twice the fuel would be 100% more. dmdicks is right, 30% is about right.

As for the dyno, it depends on what the customer thinks is "acceptable". The word here is SUBJECTIVE. For the true racer, there is simply no replacement for dyno tuning and track testing. Period. For the guy that wants to save money, give them an acceptable yet not optimal street tune and let them know the drawbacks of doing so. It's ultimately the owner's choice. There really is no right or wrong here.

Carb comment? Where did THAT come from? wink1.gif

As far as the OP's question, compression improves your engine's thermal efficiency and its output, but the risk of detonation is significantly higher. You can calibrate EMS maps to run surprisingly high boost on surprisingly high compression without detonation, but the drawback will be EGT. The things you have to do to keep the high compression motor out of knock will generally increase EGT. As you increase either boost or compression, you generally increase EGT.

The things you can do to drop EGT:
-race / high - octane fuel with the corresponding changes in injector pulsewidth and spark timing
-lower compression
-lower boost
-richer mixtures (only to a point...don't drive it to misfire)
-increase spark timing (once again, only to an obvious point)
-reduce the engine's VE. This is probably easiest through cam timing changes.
-reduce exhaust back-pressure
-combustion chamber redesign that improves detonation characteristics

That last one is what the OP might want to think about. Shaving the head has the side effect of very aggressive quench zones in the combustion chamber. Do it too much, and this can actually INCREASE detonation potential due to the incredibly fast air movement at TDC.

LASTLY: Something to think about. The Prius runs a static compression of somewhere in the 14-ish range. How does Toyota get away with this? They use a VERY long duration intake cam that doesn't close the valve until part-way up the compression stroke, giving an effective compression ratio of roughly 9, but an expansion ratio of ~14. That is the best of both worlds! You have the improved thermal efficiency without the detonation potential. I would love to see someone apply this to a race motor some time.

 

Cool thread, some good info in here.

Considering what I have been running I figured I should put a post in here...

I have been running 15 PSI out of a GT3071R for about 20 months now, I think somewhere around 10-12,000 miles. And I drive the car HARD. I have blown up 2 transmissions to prove it lol. My ignition timing is probably borderline explosive, but I like the risk and the power. Honestly I have been very surprised I haven't blown it up or scorched a piston yet. Although my combustion chambers are smooth as butter and I have better quality valves as well (custom Manleys). I told the machine shop I was going to boost when they were doing the head so they selected valves for that. I don't think the exhaust valves are sodium filled or anything, but they may be made of a more durable alloy or something, not sure. They smoothed out the hot spots in the chamber and did substantial bowl work which I'm sure helps with detonation and flow, maybe thats part of my secret with the high boost and compression?

In my N/A days I had the head shaved .007" and replaced the headgasket with the beta2 gasket which is .010" thinner if my measurements are correct?

That means I have theoretically reduced my combustion chamber height by .017". What that equates to in compression ratio I am unsure, but I would guess maybe .2 or .3 of a point???

So as long as they don't go shaving something like .020-.030" off the head (which seems a bit excessive) you should be fine to boost later on.

I must say though 15 PSI is the absolute limit with 93 octane fuel. If I add more, which I have, up to 18, it actually gets slower due to detonation I am assuming, either that or the rings can't handle it.

I think at this point I should be putting down around 300 whp. I put down 268 about 15 months ago on a more conservative timing and fuel map with different cams and cam timing. The car feels much faster now than it did then so...

I say go for it! High compression and decent boost is a winning combo! Although I plan on rebuilding the engine with rods/pistons/etc. and running hopefully 25 PSI on pump gas, might need some water meth for that. But I may also do water meth before the rebuild to try and get some more boost out of her without detonation. Either that or some E85, maybe both!!!

So I need to replace the rubber fuel line from the firewall to the fuel rail if I want to run E85? Thats it? I already have the walbro and 870cc injectors w/standalone so no problems with fuel quantity lol.

Thanks and good luck bra!