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-   -   Timing table change when going to higher CR? F vs FT Pistons (https://forums.turbobricks.com/showthread.php?t=349582)

thelostartof 06-06-2019 01:18 PM

Timing table change when going to higher CR? F vs FT Pistons
So I have gone from a FT block to a F block so my CR has just bumped from 8.7 to 9.8. Along with this I added a lighly ported 530 with larger intake and exhaust valves.

With this change what kind of advice can ya'll give on tuning down my timing map to help keep this motor in one piece. I know ideally I should throw it on a Dyno and tune it that way.

This is my timing map from when I was running it on my FT engine. So far I have been driving the car @ 9psi with this timing map without any issues. I am wanting to start turning the boost up to 14psi and get things double checked before I turn the boost all the way back to the 26psi it was running. When the car was running it used this map in 110+deg weather running 25psi without issues on the same e54 fuel that I am running now and it made pretty good power, fastest it had ever been.

The car sees only E54-E70 fuels with a gallon of 91 pump every 3rd tank to help keep things clean.


linuxman51 06-09-2019 09:21 AM

whew man with E, you really really need to hit a dyno to know for sure. it may not need anything, it may need several degrees pulled, hell it may want some. you could do runs at the track and compare datalogs and get a decent idea if you can control the runs, or go do some 2nd gear pulls somewhere on a long straightway, and overlay the logs, and that might get you close.

thelostartof 06-09-2019 12:18 PM

Ha, well that doesn't help, I guess I will be setting up time on the dyno after I get someone local who is better at MS tuning and timing tables.

I just failed emissions yesterday for High nox, 2.9 out of 2.5. I have a feeling my 15.9:1 cruise AFR's along with my not warmed up enough cat (only 5 mile drive to testing) was the issue.

So I pulled a little timing out, richened up afr's back to 14.8:1 and tomorrow I will drive it to work so we shall see if that helps.

So when looking at the logs what am I looking for to know if the timing is to advanced or not enough?

linuxman51 06-10-2019 11:17 PM

you don't look at the logs unless you can overlay two pulls that are exactly the same and compare the differences (rate of acceleration, etc), that's one reason why dynos are great. the other is you can get independent feedback on whether or not a change made a good difference.

klr142 06-20-2019 05:39 PM


Originally Posted by thelostartof (Post 5959320)
The car sees only E54-E70 fuels with a gallon of 91 pump every 3rd tank to help keep things clean.

That seems like a relatively large range of octane on your fuel if it's not exactly one number. I've also heard that what pumps advertise the fuel being doesn't necessarily mean it is what you're getting. If you tuned for something specific, you might end up having problems when the next tank is not quite as high a mixture of ethanol.

You probably already know this and for all I know, you may have a sensor or something that is helping you or your engine management keep an eye on it... but I figured it was worth throwing out there.

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