heres a link with the answers to all these questions. It should give you a good understanding of the concept of tunning, It did for me.



http://sdsefi.com/tech.html

 

I gotta go to work, but when I come back I'm gonna start going through all of that.

 

Detonation is simply combustion not caused by the spark plug, is it not? It is caused by hot spots. Higher octane burns slower and takes more heat to ignite thus reducing detonation.





I'm sure there is more to it than that, but I believe the above is all true.





Maximum Boost by Corky Bell is an incredible read.

 

pre ignition and detonation are different.



pre ignition is when the mixture lights off of something other than the spark plug, ie a hot spot. its basically normal combustion at the wrong time



detonation is when the air fuel mix explodes. a normal burn is relatively slow, explosion has a shock wave that breaks things

 

This is one of those subjects where a little knowledge can be dangerous...



I cringe when I see people trying to hit a target "number" and expect it to work or be safe.



All these numbers are used as guidelines, and I do not recommend them to be set-in-stone rules.



Due to variances in EGT sensor / gauge and wide-band / UEGO manufacturing and engine / exhaust configuration variances, you are going to get slightly different results from different set-ups.



Exhaust design can induce weird resonances and turbulences that can throw off readings that would normally look safe but in reality it isn't.



Increased experience will help you know what's safe and what isn't.

To give you a recent experience, we're trying to tune a 20B NA using an Defi (Farenheit) EGT gauge. Probe is about 20" from rear rotor and over 25" from front rotor. The EGT's don't go over 1200F, but I know it's losing power due to it being lean. 1200F is waaay too cold, and we're trying to figure out why this is the case. The engine seems to make best power at around 1000F to 1050F. Now, if I recommended this to everyone, you guys would typically be running very rich.



Wide-bands can only aide you in adjusting fuel. You cannot use the wide-band to adjust ignition timing. This is why I prefer EGT gauges over wide-bands for total tuning.





-Ted

 

thats a good example



on the its car we ended up at 22btdc@wot from 2000ish to the power peak at 6500, then we were able to go to 26btdc and it gave us a very broad power peak.



suprisingly fuel didnt do anything for power as long as it was leaner than 12.8. we went from 12.8 to leaner than 13.5 with less than a 1 hp difference in power. this is wierd but good, cause if we run it lean and put in the s5 tank we eliminate a pitstop during the enduros

 

After dynoing today it has become painfully obvious that I need a lot more work on my maps. I cant complain I pulled 327RWHP with a T-04E at 1 bar of boost. My AFR was 11.5 across the board during boost.



But I know there is more there. I need to look at my timing maps and post up I would love to know if there is some room for improvement.

 

Please do post them up Jim.

 

I read a post recently from a guy who is going through that EFI University thing mentioned in SS or SCC mag, and they did a quickly comparo on two well-known wide-band systems, MoTeC and Autronic. These are not some of the "cheaper" wide-band kits available now but cost significantly more.



The engine was a Porsche 3.6 or 3.2 liter flat 6. Wide-band probes were positioned at identical lengths away from the exhaust ports in the exhaust paths opposite of each other in the pipe. The difference in AFR readings were 0.3! I think the absolute numbers were 12.0 versus 12.3 - something to think about.





-Ted

 

so like the sensors were facing each other in the pipe?