im running bbc with a s475 and was wanting to get opinions on the air fuel ratio .I run e85 non intercooled and have run 10-11psi and will bump it up to 13-14 I for some reason thought that on the lambda scale if I was at .82 or so I would be ok but have heard it could be starting to go lean.What kind of lambda reading should I be looking for with 14psi...I run a magafuel 500 pump with a boost ref magnafuel regulator.I run a blow through carb and I monitor my a/f with a lm2 box.I start at 36degrees timing and after 4psi I take out .7 degrees up till 32 degrees then stay there..any opinions are appreciated...thanks

 

Wholly lots of timing batman..


I run e85 and set closed loop on system into lamda and aim for .8 at low boost below 10 and .75 to .73 above 10psi..

Also I'm only running 16-17 degrees by 18 psi ish..
By 25 psi I'm at 15 degree

Granted this is a modular motor and react very differant to timing.. Than what you are running..

I also run a 7 heat range ngk plug..

I would back your timing down.. And put more fuel to it above 5 psi..

 

Lambda is the same regardless of the fuel you run. .82 is fine, but on the lean side of peak power. I'd shoot for .78 or so. How did you end up at 32* total timing?

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I actually start at 35 and at 4psi start taking out timing.I take out .7 degrees per psi until I reach 32 degrees.This is all trial stuff.I know a my normal bbc without turbo runs best somewhere around 34-35 degrees timing.I keep that timing at first then start taking it out after the boost..I went with 32 based on what several people told me about timing and e85 on a bbc.A couple said that they wouldn't go below 31 on a bbc on e85..What im doing is not based on a lot of experience of my own just some trials..Im running a blow through old school setup so not a lot I can do to control boost launch etc.If I leave the line on transbrake with zero boost and the boost comes in pretty fast since im running 454 cubes on a s475.I know on the ls stuff you guys hardly run any timing but the old bbc like more timing and on N/A bbc I have run as much as 40 degrees depending on head configuration

 

this is my second time out with this combo.Im just getting into the turbo stuff so have a lot to learn..This pass was 6.28 at 115 in the 1/8th.I have a 3.50 gear so im set up for the 1/4 just haven't got to run the 1/4 yet https://www.facebook.com/joe.quinlisk/videos/10205753794316902/?fref=nf

 

What plug heat range are you running..
I would back timing down.. And make some runs

 

I can easily see a big bore, big cam, and slow burning head design requiring a lot of lead. Not saying your numbers are wrong or right. Just curious how you arrived at 32*. Did you tune by MPH at a track? Dyno? If you drop it a degree or two does the power/MPH drop significantly? Reason I ask is at lowish boost you can run a lot more advance than is “optimal” without detonation. For example… I could run 27* on my old 3.8 v6 with zero knock at 15lbs. Dropping timing down to 21* net me less than .5 mph drop in trap speed. Not worth the additional 6*. However dropping to 20* from 21* cost me roughly 1 full MPH.)

I’d suggest approaching your tune a little differently with turbo engines. Instead going with a set timing amount and slowly upping the boost, I would drop your timing to a known overly safe level. Then dial in your AFR and desired boost level first. Lastly bump timing a degree at a time and watch the gains. Stop advancing when you stop seeing the usual gains. If I don’t pick up right around 1mph at the track I stop advancing. You aren’t going to “hurt” anything by running to little advance. I’m not saying less is better either, U may end up at 36*. . Give the engine what it wants… it will tell you when it’s had enough advance.

Also from what I’ve seen personally and read, E85 requires very little if any additional advance compared to “pump gas”.

Good luck! And show us same dang pictures already!

 

im game to try different things.Im going to go up 2 jets sizes next time out and will take out a degree or 2 to see how it responds.Im running a autolight ar134 racing plug.Alot of what im doing is from my old e85 N/A setup on what it likes as far as timing and plug style.The turbo is all new to me and I just built my first one a few months ago over winter

 

Very cool, can't go wrong with a BBC! We ended up peaking on the dyno at 42* with the last NA E85 BB mopar my buddy built...cam was too big for that combo, but thats what it wanted. Turbo stuffs a whole new ball game though!

 

with my old e85 engine 34-35 degrees ran the fastest ets.That's why I start at 34-35 and take out timing with boost down to 32 degrees.Are you saying that at 13psi that you don't think I need to drop timing down to 32 but keep it close to the total timing I have at 34..The 32 isn't something I came up with based on a lot of runs it was suggested to me..I just took out .7 per psi down to 32 degrees then left it at 32 at full boost..Im going to try more and more changes now that im getting slightly comfortable with the turbo but was looking for some good advice..thanks again for any info

 

also by reading you post do you not take any timing out of your combo at boost..Do you find a number that gets you the fastest time and then leave it there without taking out any timing...Still trying to figure this out

 

Sorry, I'm use to EFI and having a timing table to throw my desired timing number in at X load and Y RPM. What retard setup are you using?

On the LS stuff I literally flat line my whole damn curve above 10 psi to say 12*. Dial in AFR and boost. Im my case 11.5 and 21lbs. Then make a pass at 13*, 14* 15* 16* etc... until my MPH levels off. Then I go back and adjust the curve down a little at peak torque and up a little over peak torque.

You end up with something like this in the end.
100KPA is 0psi
300KPA is 28.8 psi

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thank you so much for you info.I will definetly give what you have suggested a try.Im still alittle lost and appreciate your help...thanks again