Bandimere 4/20

[rao]

This is good to know. So there are no compression limits with e85 either? That is certainly good news. There is a lot of power being left on the table since you can easily change to say a 20:1 compression ratio (or a lot more, since it can't knock ther is no real limit) and start making some real power.

 

The real question is why bother with an intercooler at all, since e85 can't knock or be heated or cooled

 

Think of the throttle response you all could have without an intercooler in the way!

[mwiener2]

You have too much free time

[SSpeed]

Think of the throttle response you all could have without an intercooler in the way!

 

Early 80's Dodge Daytona!

 

http://t0.gstatic.com/images?q=tbn:ANd9GcTnduanXKkI_vF_4nPdLN7Hrhp29RKmGjCPA8MbnwppS66b6Gr7qw

 

However, you may need to retune the ecu separately for each injector...

[LittleBlueGT]

Agreed that is real knock. That's why I am not doing much to weaken the role of FBKC in protection of the motor under those conditions and that is also why I made slight adjustments to timing, boost, and fueling in the affected spot.

 

The shift-knock probably isn't.. and even if it is it is only due to very transient conditions created during or just after the shift... I feel that the motor can resume it's demonstrated safe full-timing jaunt through 2nd-3rd gears and shouldn't have timing penalized for that kind of knock, whether real or not.

 

 

I can't see it being anything but real knock, nothing else makes sense.

 

Of al the subys, your would suffer from the most heat problems, smallest scoop, not very efficient comp wheel (like mine) smaller TMIC, etc.....

 

I agree with you that shift knock is likely not, or if it is, you can resume normal timing very quickly there-after.

 

I would be leary about making the FBKC load range start at 2.0 load with anything but E85.

[Legend]

You and I have talked about this, I've always gotten fairly bad shift knock, or more accurately "mash knock", on every tune I've had, even stock....

 

Do you think this change is safe for all situations?

 

Feedback Correction Minimum Load - changed to disable below 2.0g/rev (was stock value of 0.55g/rev in prior map)

 

Looking at some of my logs, setting it to that number would basically disable knock correction on throttle up until I hit about 12psi...

 

I haven't flashed the new map that I built this a.m. with all the little changes to deal with both of my little racing problems. This is the one value that I want to sleep on first and/or invite more commentary. I will probably proceed with this change though.

 

I briefly looked through 5-6 WOT logs in various gears. If I make this change I'd be disabling FBKC under 2500-3200rpms, depending on gear... and I couldn't find any instances of boost greater than 10-10.5psi where load was less than 2.0g/rev. Mild conditions, especially for E85.

 

Keep in mind there are what.. 3 different types of knock mitigation (FLKC, FBKC, IAM)... even though I'll be neutering FBKC under 2.0g/rev, both FLKC and IAM will continue to be alive and well throughout the entire powerband. If I did develop a low-load knock problem, it's not like I'd be screwed... FLKC would just decrement the cell. I'd much rather have a localized dip in timing than all through 2nd and 3rd gear.

 

And I'm not invoking this strategy alone. I've already got soft landing spots for fueling and timing in addition to generous tip-in. None of it has made much, if any, difference... which makes sense since the microphone is likely picking up drivetrain noise, not knock. My motor does not deserve to have timing and resultant power held back.

 

My first pull on Harvey's dyno was 335whp... I added 2 degrees across the board and instantly 343whp. 4whp/degree = good increase. I added another 2 degrees and got 345whp peak but most the curve was the same. 1whp/degree = poor increase and decreased margin of saftey, so I backed off to the 343whp curve. Point is, if I'm running with 4-6 degrees less timing than tuned, I know for a fact I'm down 10whp at a minimum... maybe 20whp(?) Not cool.

 

Anyhow, do I "think it is safe for all conditions"? On E85, safe enough, I think.

[NSFW]

Legend, if you're tuned with open source I'd be happy to take a look at your tune and see if I can help.

[LittleBlueGT]

My motor does not deserve to have timing and resultant power held back.

 

 

My first pull on Harvey's dyno was 335whp... I added 2 degrees across the board and instantly 343whp. 4whp/degree = good increase. I added another 2 degrees and got 345whp peak but most the curve was the same. 1whp/degree = poor increase and decreased margin of saftey, so I backed off to the 343whp curve. Point is, if I'm running with 4-6 degrees less timing than tuned, I know for a fact I'm down 10whp at a minimum... maybe 20whp(?) Not cool.

 

Anyhow, do I "think it is safe for all conditions"? On E85, safe enough, I think.

 

I have another theory, but I don't have the means to test it (no race gas or E85 around here):

 

On pump gas we pretty much just tune to the knock threshold, then back off a bit for safety.

 

On E85 we tune for MBT, pretty simple, right?

 

Well, on pump gas we take advantage of the timing IAT comp table to add or subtract timing based on IAT, this is designed to stay comfortably within our margins that we want for balancing the best timing we can run with a small safety margin.

 

What happens on E85? What does your timing IAT comp table look like?

 

If it adds a couple of degrees when it is much cooler outside, is that still the ideal for MBT? If it subtracts a couple when really hot, is that still the ideal?

 

I would think a bit of E85 20F and 120F dyno time would tell you right away.

 

Just a thought.

[mwiener2]

Harvey's dyno is easy to do that... go on a 20F day and then 180 days later go on a 120F day

[Legend]

On pump gas we pretty much just tune to the knock threshold, then back off a bit for safety.

 

On E85 we tune for MBT, pretty simple, right?

 

NOT simple, unfortunately. Road tuning on E85 is not as easy as road tuning for gas. You're right... on gas you can road tune, find the knock threshold, and back off. When road tuning with E85, you really have no precise idea where to stop advancing timing because you can go beyond MBT and still won't knock. The logs and/or airboys don't have enough resolution to accurately dial in timing. The scales are tipped much more favorably towards a dyno tune (vs. road tuning) with E85 because of this. I know you know this but I just had issue with the word "simple".. anything but simple. Once on E85, a dyno becomes an even more valuable tool.

 

What happens on E85? What does your timing IAT comp table look like?

 

If it adds a couple of degrees when it is much cooler outside, is that still the ideal for MBT? If it subtracts a couple when really hot, is that still the ideal?

 

I would think a bit of E85 20F and 120F dyno time would tell you right away.

 

Just a thought.

 

Here is what my timing IAT comp table looks like...

 

http://beeez.com/lgt/timingiat.jpg

 

About stock, except my table has -1.05 at 86F whereas the stock table has zero. I have never given much thought to this table. My gut tells me with E85 the table really ought to be flattened quite a bit. You're right the only way to find out would be dyno time at different temps.. and since that isn't realistic we can just speculate. I think I will flatten it some. None of this will have any impact on my 4th gear collapse syndrome since it is IAT instead of charge temp and also I've had this phenomenon racing in both 45F temps and 90F temps. But it is a good question you raise..

[Legend]

Asked the question on the E85 forum...

[mwiener2]

 

Your gut is right.

 

We can artificially raise the temp as far as the car is concerned. If you want to do some testing, PM me and I'll go over some procedures we could do.

[LittleBlueGT]

I flattened my table a fair bit with the FMIC, and I tend to think your table is not the best for E85.

 

How much dyno time would you need, 1 hr twice? I would do it.