e85 timing sweet spot?

TurboTPI

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Is there a certain degree that is the sweet spot for e85? Or does every build like a different timing spot? Im at like 22-23 degrees currently with no KR. I feel like it might be too much though. I ran 19 degrees for awhile and it almost felt stronger then. But its been really hot here and that really kills power on unintercooled M90 cars. What are your guys thoughts/experience's? Thanks.
 

1quick

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I always ran more boost and less timing, I had an unintercooled m90 car on e85, it was a l26 bottom end so it was a little more compression but I ran stock timing and a 3.0 pulley seemed to like that
 

willizm

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I’ve found that there is a point of diminishing returns with timing on e85. For me it was around 21*, I just would add more boost
 

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Blower cars like 18-20, anything over that doesn't help and could chip a piston if the car is heat soaked.
 

P40E

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Start by using a consistent fuel by checking content . After you establish that , get on a dyno . Then adjust and re dyno .
 

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Wut? Why? That would cost almost as much as the car is worth..
 

HellPIG

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I run 21 on E85
I run 14 on E70

There is some "play" built into that obviously.

In this weather, the car yanks timing regardless when IAT's get to a certain point.

I see short term knock here and there, but I watch it close. This motor hates certain RPM points, high load low rpm. Loves being hammered from low MPH, loves anything from a roll over 4000-4500. I see 1-1.5 degree here and there around shift points, which makes me think it could be false. I saw 4 degrees last night on a downshift.
 

b4black

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Every cell in the timing tables has a sweet spot, or optimal timing for Maximum Brake Torque (MBT) . The cells you are interested in at WOT reach Knock Limited Spark Advance (KLSA) well before they get to the sweet spot. I added 4° to my entire high octane table and then another 4° through the AFR adder. So that was about 24° total at WOT - with zero knock. I saw a 1 mph gain going from 16° to 20° and another 1 mph going to 24° (back to back runs).

I firmly believe if you are not knocking, your pistons are safe. I ran this way for several years and plenty of trips down the track. E85 with an IC and headers.

I later tried more boost and less timing. I went from a 2.9" pulley to a 2.7". After maxing out timing to the edge of knock (18°?), I found I was running pretty much the same ET/mph. For my car more boost w/ less timing was the same as less boost w/more timing.
 

GTPpower

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You should pull timing back some. You are flirting with disaster.

On e85, a good rule of thumb is stock timing down to a 3.0 pulley. As you drop below a 3.0, turn timing up. I would keep it at or under 19°, unless you like to replace motors.
 

TurboTPI

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Thanks for all the input guys. I didnt realize i was running that much timing till i scanned today. I did a few pulls today in this high heat just to make sure i didnt have any KR and in the scan i realized how much timing its at. I really dont want to have to put another set of pistons in this thing, so im going to pull timing down a couple degrees. Im planing on going to the dragstrip next weekend, im running a 3.2" now, im thinking of putting a 3.0" on and see if it mph any more.
 

b4black

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Here are timeslips. Left to right is 24°, 20° and 16°


24° is not too much. Timing or boost do not chip pistons. It's knock. The cylinder pressure of knock as way, way higher than timing or boost can produce.
 

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And what happens when the car is heat soaked? It knocks, with such aggressive timing, it WILL chip a piston.

BTW, I trapped 99mph in a stone stock 4dr GTP with 18 degrees of timing on pump gas. NBD.
 

TurboTPI

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And what happens when the car is heat soaked? It knocks, with such aggressive timing, it WILL chip a piston.

BTW, I trapped 99mph in a stone stock 4dr GTP with 18 degrees of timing on pump gas. NBD.
That just irritates me hahaha. I trapped 103mph with all the shit i have done. shoot me now
 

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My other GTP was bolt on's with an xp cam and I was able to get 113mph out of it non-intercooled on E85. Best trap on pump gas I got was 108mph.
 

b4black

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And what happens when the car is heat soaked? It knocks, with such aggressive timing, it WILL chip a piston.

BTW, I trapped 99mph in a stone stock 4dr GTP with 18 degrees of timing on pump gas. NBD.
With E85 and an IC, I managed heat well. I heat soaked the car may times at the track and would see 1-2°KR. NBD.


Tell us more about how you trapped so well. Most stock 3800SC trap in the low 90's, so you must have done something better than the rest of us besides bumping timing up 2°. Was it all driver, or ?
 

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He's not running a I/C, much different situation.
 

1quick

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I trapped 105 with just a pulley down pipe and drop in k&n on the stock computer and unleaded race gas to combat knock but this was back when the cars were new and a lot tighter than they are now
 

GTPpower

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Here are timeslips. Left to right is 24°, 20° and 16°


24° is not too much. Timing or boost do not chip pistons. It's knock. The cylinder pressure of knock as way, way higher than timing or boost can produce.
It looks to me like the 20° tune was the best. Highest 1/8 trap and not as good of a 60' as the 24° tune. I'm also assuming that the 24° pass was made earlier in the day, which likely would have had a better DA.

I've seen a lot of people pop motors over the years from that much timing.
 

b4black

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No way the 20° was better than the 24°. I ran 20° for quite a while before bumping up to 22° and 24°. Car was definitely faster with 24°. I just did those three runs one day to show the difference.

Timing won't hurt the engine if you keep it from knocking. I logged KR every run.
 

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I ran a 2.6 pulley on E85 with 26 deg and the knock sensors disabled.

send it
 

GTPpower

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No way the 20° was better than the 24°. I ran 20° for quite a while before bumping up to 22° and 24°. Car was definitely faster with 24°. I just did those three runs one day to show the difference.

Timing won't hurt the engine if you keep it from knocking. I logged KR every run.
According to the time slips, the car isn't any faster on 24°.

Many people have lost engines with high timing and not even a blip of kr.
 

b4black

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Um, 101.51 is faster 99.82.

Those were just an example. I already said I had plenty of other slips to back them up. Car was consistently faster at 24° than 20°. Why are you arguing this?

On e85, a good rule of thumb is stock timing down to a 3.0 pulley.
I'm very glad I didn't listen to you..
 

GTPpower

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Um, 101.51 is faster 99.82.

Those were just an example. I already said I had plenty of other slips to back them up. Car was consistently faster at 24° than 20°. Why are you arguing this?


I'm very glad I didn't listen to you...
You are missing a few pieces. Your DA was better on the 24° pass. So, it should trap higher. You also cut a better 60ft on it. All that considered, there is no concrete evidence that 24° is any better than 20°.

The car basically ran the same. It's easy to see that it's not worth the added risk.

It also appears that our knock sensors do not pick up preignition very well. They are great with detonation, but since e85 is only about 94-95 octane, preignition is much more likely.
 

1quick

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You are missing a few pieces. Your DA was better on the 24° pass. So, it should trap higher. You also cut a better 60ft on it. All that considered, there is no concrete evidence that 24° is any better than 20°.

The car basically ran the same. It's easy to see that it's not worth the added risk.

It also appears that our knock sensors do not pick up preignition very well. They are great with detonation, but since e85 is only about 94-95 octane, preignition is much more likely.
from everything ive ever read e85 is around 104-105 octane, unless its made with good gas as the 15% gas then its around 112
 

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