Ford Mustang Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
1,579 Posts
Discussion Starter #1
Guys, looking to hear how much timing you are able to use safely on 93 pump gas with the PI motors.

Timing seems to be a myth with the mod motor people. Which I get, being there is no dizzy to check it.

My last street car was a 331 9:1 TFS heads with 10# and a air to air intercooler. I was able to run around 20* total timing with that setup.

I'm not sure about these PI motors. I've heard people pulling back to like 10* which seems way to far for 10#.

Is there a relation with the heads and their chamber/quench area that you must run way less timing than the winsor 302s?
 

·
Registered
Joined
·
4,126 Posts
All I can give you is what I experienced with one pull on 91 oct so hopefully others will chime in.

With 91oct I got a LOT of knock (Safeguard Knock detector) with 11* at only 7psi of boost. I only made the one pull so when the knock detector went off then I added meth inj.

ks
 

·
Registered
Joined
·
4,126 Posts
Yea man I remember you telling me that. That's crazy low timing at only 7#. Maybe that 91 you had in there was some crappy fuel straight out of the pump.
I don't think it was worse than any other 91 around the city but this is only speculation on my part. Even if someone else posts their results how do they KNOW the motor wasn't still knocking unless they had electronics to monitor the knock? Maybe they didn't blow it up but it could have still been knocking. How will you know that the 93 you get is truly 93?

I'd still invest in a Safeguard if running 93 b/c then you'll know exactly what's going on in those cylinders..

ks
 

·
Registered
Joined
·
1,579 Posts
Discussion Starter #6
Right now my turbo is full spool at 4000rpm. My timing is 16 at this point and is pulled back 2* beyond 5k. My plugs show no signs of detonation and I can't see any heat line in the ground strap at all.

So, my timing is a bit higher than yours was, and I'm at 10# boost. Granted there is a hundred factors that determine what a perticular engine likes, but you see where I'm going with this...

I know there are a million S-trim mod motor stangs out there, hopefully they will chime in.
 

·
Registered
Joined
·
486 Posts
Right now my turbo is full spool at 4000rpm. My timing is 16 at this point and is pulled back 2* beyond 5k. My plugs show no signs of detonation and I can't see any heat line in the ground strap at all.

So, my timing is a bit higher than yours was, and I'm at 10# boost. Granted there is a hundred factors that determine what a perticular engine likes, but you see where I'm going with this...

I know there are a million S-trim mod motor stangs out there, hopefully they will chime in.
I was running 18.4 total timing on my BB347 and added 2* and picked up 4/10 on a aborted pass. still have not seen any heat in the plug straps yet. next outing I will be adding 1* at a time till I see something to tell me I have gone to far. Not sure about how much timing effects a mod motor but will know soon since a friend is building his car to go low 8s.
 

·
Premium Member
Joined
·
4,771 Posts
Usually much less than a 302w based engine. Use 26 total as your max and subtract 1* for each pound of boost, then subtract 2 more for safety, then make a pull and shut down, read plugs, add 1* at a time till heat on strap is near the bend.
 

·
Registered
Joined
·
122 Posts
Its flame propagation and flame travel across a tiny piston, homogeneous mixture due to in the cylinder motion, piston dwell time at TDC...all contribute to how the engine responds to advancing the spark timing. A bigger piston will need more advanced timing. A shorter stroke will need more timing. Poor in cylinder mixture will need more timing and so on...

Advance timing is a clear indicator of inefficiencies or a crap ton of forced induce oxygen.

Just ideally saying....
Talking out of my ass here
 

·
Premium Member
Joined
·
4,771 Posts
Its flame propagation and flame travel across a tiny piston, homogeneous mixture due to in the cylinder motion, piston dwell time at TDC...all contribute to how the engine responds to advancing the spark timing. A bigger piston will need more advanced timing. A shorter stroke will need more timing. Poor in cylinder mixture will need more timing and so on...

Advance timing is a clear indicator of inefficiencies or a crap ton of forced induce oxygen.

Just ideally saying....
Talking out of my ass here
No you're not, you are quite on the money.
 
1 - 10 of 10 Posts
Top