So a guy emails me asking for help with his project. He has a 4.7L stroker and put a M112 supercharger on it. He asked me and wanted me to send him the fuel and timing map/file for the Split Second FTC1 with the 7th injector as a starting point.

I asked him, SS should have preloaded the FTC with a base tune/file.

I did ask him a few questions- 'it depends on a lot'.
-What is the base HP of the stroker?
-What size is the 7th injector?
-How much boost?
-What is your pulley ratio? Crank and SC pulley diameter?
-Are you 'blowing' thru the SC with the 7th injector?
-What size are the other stock 6 injectors you are using?
-What tune do you have on the stock ecu for the stroker?

I also emailed him some tuning highlights.
-at 5000rpm, 1 engine rev =12ms
-the SS box fires the 7th injector 3x/1rev =4ms/injector firing
-80% duty cycle, max injector on time is 3.2ms at 5000rpm
-the injectors have a 'latent' time, also known as dead time, offset, lag time, latency. Average is 0.8ms
-So really only have 2.4ms of on time at 5000rpm
-it requires about 0.7lb fuel/HP
-60hp gain from the SC requires a 60lb/hr 7th injector, +100hp requires 100lb/hr
-any more HP gain would require another injector, a 7th and a 8th.

Sample fuel table for SS FTC1, build the table
-1ms at 1psi and 1000rpm
-3.2ms at 1psi and 5000rpm
-3.2ms at 6psi and 5000rpm, then autofill in all the other table values
-above 6psi 3.2ms, above 5000rpm 3.2ms to finish filling in the table

Sample timing table for the SS FTC1, build the table the same way as fuel table
-1degree at 1psi and 1000rpm
-3degrees at 1psi and 5000rpm
-6degrees at 6psi and 1000rpm and 5000rpm, then auto fill the table.

I didn't send him any fuel or timing tables. I didn't know enough about his specifics to be able to recommend/send him any tune/tables.

I didn't hear anything back from him.
I emailed him if he got his tuning squared away?

He emailed back,
'We busted a piston with detonation. SS box wouldn't pull enough timing to keep it away from detonating with the motor we have. Going to a custom tune with SCT programmer and the software to make changes ourselves. Going to use 6- 54lb/hr injectors and get rid of the SS box. I think the motor had too high a CR at 10.8:1 for the 20* timing retard to help. Lowering the CR down a bit into the high 8s'.

How much boost?
'9 pound boost with the M112'.

I emailed him-
-Sounds like too high compression ratio and not enough fuel and octane.
-Custom forged pistons are available with any CR, dish and pin height.
-Your motor should be about 275hp and 9pounds of boost will add at least 125-150hp. You will need enough fuel for 400 total HP.
-54lb/hr x 6 =324lb of fuel, that should be enough fuel. That's how much total fuel needed with the 7th injector.

 

Lessions Learned/ His Mistakes

-Very ambitious project not fully understanding SC and tuning
-4.7L and M112 SC
-10.8:1 CR and thinking that you can SC that
-No Wide band O2 sensor required for tuning
-9 pounds of boost
-Not enough fuel and not enough octane
-thinking that retarding the timing 20* would be a tune and fix his issues
-didn't go slow and check for detonation, AFR and then proceed from there. 1pound of boost and test, then 2 pounds of boost and check, ...
-at the first hint of detonation, GET OFF THE PEDAL!! You can survive short mid detonation
-Do not just WOT it and see how much boost and blow a hole in the piston

Anyway just wanted to share how NOT to SC a jeep engine.
It's not Rocket Surgery but a bit more than a Caveman can do.

 

Today I emailed him-
M112 and 9 pounds of boost and 6-54lb/hr injectors tuned with SCT, What are you going to do about your Intake Air Temps?

With 9 pounds of boost , you will be adding 150-200* to your already high stock IAT of about 120*. You're looking at IATs of 270-320*. At that high of IAT, you will still detonate no matter how good your tune is.

Any plans for an intercooler to lower the IATs to a more reasonable level? 150-180*, 200*max.

What year jeep is this engine/SC going into? This also makes a difference.

 

'99 TJ.
For intercooling, he is now planning on running the Snow Performance stage 2 boost cooler.
Also spraying 100hp wet kit.
Shooting for around 500HP.

 

I think that statement says it all.

 

Blower pistons are usually ~ 8:1, a little research can save a lot of money.

 

8:1 is more old school thinking. Thinking is, low CR and more boost is 'lazy' when off boost. Higher CR makes more power and is 'snappier' when off boost and with lower boost applications, less than 10-11 pounds, actually makes a better performing engine.

Stock 4.0L is 8.75:1 and works fine. We run 9.25:1 with custom pistons with 0.043" quench.
Aluminum heads can run 10:1.

 

a jeep engine is no different than any other engine. not knowing what you're doing will kill anything. hell I won't go beyond bolt ons bc there is not a feasible solution for a tune. hpt keeps teasing us with jtec stuff.

 

I wish this engine build well.
4.7L, M112 SC, 9 pounds boost, Snow Meth injections and Nitrous.
Shooting for 500HP.
All that's missing is the ported edelbrock aluminum head.

 

Could always drop 2k on a haltech elite and have the ability to tune however you want.