|
Author
|
Topic: pi swap and 100 octane ??
|
saclve
¯
Member # 13280
|
posted
 
 
Ok so my 98 gt has a full pi swap with fresh set of heads and 4.10 gears 5 speed and was wondering since I have the raised compression would running couple gallons of 100 oct. Unleaded fuel yield any extra whp ?? Only for testing at drag strip
Posts: 276 | From: sacramento | Registered: Nov 2013
| :
|
|
wilit
Mustang Messiah
Member # 3367
|
posted
Nope.
--------------------
"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
| :
|
|
Tom Renzo
¯
Member # 13165
|
posted
You can mess with the timing with higher octand and pick up a couple of tenths. Keeping the engine from detonating and the advantsge of more timing is a good thing. I would not hesitate to do it .
--------------------
I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
| :
|
|
SLOW95GTS
¯
Member # 10365
|
posted
if you had like 12.5-1 compression yes, I bet your only in the 9.5-9.8.1 compression range with the P.I swap.
--------------------
1995 Mustang GTS 5.0 - "minor mods"
Posts: 1199 | From: East Bay | Registered: Oct 2010
| :
|
|
Tom Renzo
¯
Member # 13165
|
posted
The compression does not control the octane requirements. The Cam and total timing does.
[ 2014-05-17, 04:40 PM: Message edited by: Tom Renzo ]
--------------------
I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
| :
|
|
saclve
¯
Member # 13280
|
posted
Well I'm picking up a sct tuner tomorrow so hope I can get a custom tune to a just all of that regardless I'm shooting for a 13.6 at track tmrw with pi swap and intake and street tires
Posts: 276 | From: sacramento | Registered: Nov 2013
| :
|
|
Pure Stang
¯
Member # 7251
|
posted
quote:
Originally posted by Tom Renzo:
The compression does not control the octane requirements. The Cam and total timing does.
So what you're saying is I can have 13.1 compression and can run 91 octane and be ok based on timing? That's actually the first time I've ever heard that.....
--------------------
HEART BREAKER
R.I.P Willie Guzman (5ltrsvt) you will be missed brother.
04/24/87 - 11/23/2012
90 lx 347 RIP
86 gt
89 lx- next project
Posts: 6497 | From: San Jose | Registered: Nov 2006
| :
|
|
Tom Renzo
¯
Member # 13165
|
posted
Depending on the sweep compression that controls cylinder pressures YES!! We run LS motors well in to the 12.5 CR areas with no issues on pump. But we have huge cams in them. The cams control the sweep, compression and in turn controls the octane. Example a cr of 8.5 can ping on high test if the timing and sweep compression is modified and they do. But some engines with correct combination of timing and sweep will not. It all depends on how long the cylinders are sealed.
--------------------
I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
| :
|
|
saclve
¯
Member # 13280
|
posted
So basically now at 10.5 or whatever compression I'm at I need to run at least91 to prevent detonation but in turn if I ran 100 octane it would currently be useless until I have my sct tuner set up and in race mode which advancessentially the timing ?
Thanks for explaining Tom reno you are full of useful knowledge buddy
Posts: 276 | From: sacramento | Registered: Nov 2013
| :
|
|
Pure Stang
¯
Member # 7251
|
posted
quote:
Originally posted by Tom Renzo:
Depending on the sweep compression that controls cylinder pressures YES!! We run LS motors well in to the 12.5 CR areas with no issues on pump. But we have huge cams in them. The cams control the sweep, compression and in turn controls the octane. Example a cr of 8.5 can ping on high test if the timing and sweep compression is modified and they do. But some engines with correct combination of timing and sweep will not. It all depends on how long the cylinders are sealed.
Interesting. Something I didn't know and ill defiantly read up on it.
--------------------
HEART BREAKER
R.I.P Willie Guzman (5ltrsvt) you will be missed brother.
04/24/87 - 11/23/2012
90 lx 347 RIP
86 gt
89 lx- next project
Posts: 6497 | From: San Jose | Registered: Nov 2006
| :
|
|
wilit
Mustang Messiah
Member # 3367
|
posted
quote:
Originally posted by Pure Stang:
quote:
Originally posted by Tom Renzo:
Depending on the sweep compression that controls cylinder pressures YES!! We run LS motors well in to the 12.5 CR areas with no issues on pump. But we have huge cams in them. The cams control the sweep, compression and in turn controls the octane. Example a cr of 8.5 can ping on high test if the timing and sweep compression is modified and they do. But some engines with correct combination of timing and sweep will not. It all depends on how long the cylinders are sealed.
Interesting. Something I didn't know and ill defiantly read up on it.
Static Compression Ratio is what you come up with when 99% of people calculate the compression ratio of a motor. It's the compression ratio with no valve events taken into account. What Tom is talking about is called Dynamic Compression Ratio. There's lots of info and calculators out there to help you figure out what the DCR is of a motor.
[ 2014-05-18, 11:40 AM: Message edited by: wilit ]
--------------------
"If a man hasn't found something worth dying for, he isn't fit to live." - Martin Luther King Jr.
Posts: 4793 | From: 37.78514° North 122.40100° West | Registered: Oct 2003
| :
|
|
Tom Renzo
¯
Member # 13165
|
posted
Exactly!!
--------------------
I spend money i don't have. Building cars i don't need. To impress people i don't know.
Posts: 557 | From: CT | Registered: Sep 2013
| :
|
|
Justfloatn
¯
Member # 11420
|
posted
Don't read into Dynamic too close with small cams. For example if you take a PI swap motor and comp 262AH cams and plug them into a dynamic compression calculator you will get a dynamic reading of 9.5 ish due to the early closing of the intake valve. Most say and engine won't run without race fuel if the dynamic is over 8.7 to 9.1. But the 8.7 to 9.1 is all internet posting garbage. I wish I had the time to find the real answers to some of this stuff.
I started looking into it because a tuner told me my compression was too high for my cams and it would not run due to dynamic compression, bla, bla. I wasted a bunch of time and stress researching the subject to find out he was wrong. Good info on Yellowbullit about the subject. Then I started playing with stock motors and PI swap motors on the calculator with the small cams. Based on Dynamic none of them would run. ![[Roll Eyes]](rolleyes.gif)
I think Dynamic is more useful with large cams due to the overlap and late closing of the intake. That is when you need to figure out how much extra compression you should build into the static compression to compensate for the camshaft.
Posts: 12 | From: Rocklin | Registered: Nov 2011
| :
|
|
Email this post to someone!
Printer friendly view of this Ford topic
