stroker ?s

[rredalty]

Got a 4.6 in the MJ. Seems to be running rich with a set of 24lb injectors and a stock pre 95 FPR and Renix pump. What do I need to do here, get more timing into it or pull fuel out? Runs like a raped ape on 110 so I'm thinking the CR won't ignite the 93 I have been running and I'm not looking to spend $5.59 gal on the 110 to drive it to Sonic for an afternoon limeade.

 

[Dr. Dyno]

What are your stroker build specs?

 

[xjbump]

I always thought unless you have more 11.0 comp. you shouldnt need to run on higher octanes. I've run a 4.7 before on 87 octane and it ran fine.

 

[rredalty]

89 block, 94 head, 4wt 258 crank w/ 4.0l long rods if I remember correctly, 4.6l, 9.8:1 comp, crane cam, port matched, 99+ intake, borla header, 62mm TB and a york 210.

 

[Dr. Dyno]

You should be able to run premium pump gas though in hot weather, you might need to add some octane booster in the tank.

 

[rredalty]

so you think a lack of ability to ignight premium and thats the need for leaded 110?

 

[Dr. Dyno]

You don't need 110. Just run premium and see how it goes.

 

[rredalty]

thats what I am running usually.

 

[BlueCuda]

Its probably running rich because the lead in the 110 killed the 02 sensor.

There is no reason to run 110 octane IMO. I have the same compresion ratio and run 87 in mine most of the time anymore.

 

[Dr. Dyno]

Its probably running rich because the lead in the 110 killed the 02 sensor.

Good call and if you have a cat, the lead would have killed that too.

 

[crusTodd]

Hey Dino,
How much 110 would you have to run before it'd damage the cat?

 

[rredalty]

o2 shouldn't matter until the ECU achieves closed loop right? The Jeep rarely sees anything over 165-170 unless it is really catching hell.

 

[gradon]

What * t-stat do you have in there(should be 195, but 180 at minimum)? o2 will be in the loop(closed) after warm-up and normal driving under 70% throttle, so basically whenever you're not stomping on it.

 

[Dr. Dyno]

Hey Dino,
How much 110 would you have to run before it'd damage the cat?

No eye deer. How long is a piece of string?

 

[Turtle]

Runs like a raped ape on 110 so I'm thinking the CR won't ignite the 93 I have been running and I'm not looking to spend $5.59 gal on the 110 to drive it to Sonic for an afternoon limeade.

Common misconception is that higher octane is better. Actually a higher octane is less volatile, so it does not ignite as easy. This is why you need higher octane for higher compression ratios. With a lower octane and higher C/R the chance of detonation is higher as the fuel is MORE volatile and easier to pre-ignite. Detonation is two flame fronts colliding, one of those flame fronts is from the spark plug, the other is from high cylinder pressures causing hotter combustion chamber temperature which can cause a hot spot that acts like another spark plug and can more easily ignite the lower octane more volatile fuel. 9.8:1 should not require 110 octane. Also there could be some sharp/thin spots in the cylinder head chamber that are glowing causing a hot spot.

Is the programming your running setup for 24lb injectors? Also I think your running cooler than needed, I would run a hotter T stat for better efficiency, a hotter engine will be more efficient and get better mileage than a colder engine. Also put a scanner on it and see if the O2 is cycleing up and down fairly fast, if it's lazy and lethargic it may be bad or not hot enough. You should also check the loop status to make sure it is staying in closed loop. The O2 needs to be at least 600 degrees, sometimes with headers and an exhaust system the O2 can get below 600 degrees at times causing it to go into open loop, if it is a 1 wire O2, with headers/exhaust your should adapt a 3 or 4 wire O2 which has a heating element in it to keep it above 600deg.

 

[rredalty]

RENIX. No tuning, no scanner and I could give 2 shits about daily drivability and fuel economy. The only time this thing ain't on the trailer is on the trail or out beating the hell out of it on the street.

 

[old_man]

I run a 4.7L stroker here in Colorado. It is set up at 10.4:1 compression. I run the cheapest gas I can find with no ping. I decked the block .025 and run a thin Mopar head gasket.

It ran rich with the Ford performance 24lb injectors. I'm a EE so I ended up fabing up a MAP sensor adjuster and dialed the mixture down. Hesco sells them for around $100 but you can find how to build them online.

 

[Dr. Dyno]

I run a 4.7L stroker here in Colorado. It is set up at 10.4:1 compression. I run the cheapest gas I can find with no ping. I decked the block .025 and run a thin Mopar head gasket.

It ran rich with the Ford performance 24lb injectors. I'm a EE so I ended up fabing up a MAP sensor adjuster and dialed the mixture down. Hesco sells them for around $100 but you can find how to build them online.

Here's the best write-up you'll find anywhere on the www, and it's mine:

http://www.angelfire.com/my/fan/MAP_adjuster.html