Started my 4.7 Stroker build today.

[-PigPen-]

Originally Posted by bajabronco

I swapped in the AEM 50-1220 E85-Compatible High Flow In-Tank Fuel Pump (340lph) last week to solve the fuel flow problem with my dying fuel pump. I was able to get back to Dyno tuning today. The top pull was 229 HP, which we thought might be borderline knocking , so I ended up going with the 227HP tune. The XJ is a lot
of fun to drive even with 37’s it moves!



Final tune I went with



So with the stroker build I gained about 80 rear wheel horse power.

That’s awesome. I’d love to see more info like this. The butt dyno always lies.

[hexdmy]

Here is the dyno data to review, I've included delta hp/tq data as well as some ecu data: intake air temp, coolant temp, injector pulse width, injector duty cycle, vss, measured lambda, commanded lambda, manifold pressure.

I tried to keep coolant and intake air temperatures consistent run to tun since the power numbers vary considerable with engine temps.







- Chris

[cal]

Now we just need to figure out a real number for powerloss in the drivetrain.

[hexdmy]

Originally Posted by cal

Now we just need to figure out a real number for powerloss in the drivetrain.

Unfortunately the only way to really know is to run a few combinations both on an engine dyno and on the hub dyno.

[hexdmy]

Just a reminder as to why you need to watch your fuel pressure. This truck had no delivery issues with the stock engine, but once the bigger injectors were installed with the stroker build, the pressure started falling off excessively.

[maxbraketorque]

Pretty interesting to see that fuel pressure begins to drop off just shortly after the stroker motor power exceeds the factory power level. The factory fuel pump is just perfectly sized. So this is a returnless system?

I am a little surprised that you set the final tune to be only a few WHP below the knock threshold on a motor with no knock sensors. Doesn't leave much room for dealing with off normal situations where the engine may be hotter. Did you tune for regular gasoline or awesome CA 91?

[RCP Phx]

Originally Posted by maxbraketorque

I am a little surprised that you set the final tune to be only a few WHP below the knock threshold on a motor with no knock sensors. Doesn't leave much room for dealing with off normal situations where the engine may be hotter. Did you tune for regular gasoline or awesome CA 91?

I don't where you come up with this stuff? The build "itself" determines all that, Chris knows what he is seeing and adjusting/accounting for accordingly.

[maxbraketorque]

Sounds like he's tuned his share of XJs, so I guess all is ok, but as I said, its surprising based on my experience with building and tuning my street car over the last 14 years.

[RCP Phx]

Originally Posted by maxbraketorque

Sounds like he's tuned his share of XJs, so I guess all is ok, but as I said, its surprising based on my experience with building and tuning my street car over the last 14 years.

I'd say your lacking on your understanding of how to properly design a build.

[bajabronco]

Originally Posted by maxbraketorque

Pretty interesting to see that fuel pressure begins to drop off just shortly after the stroker motor power exceeds the factory power level. The factory fuel pump is just perfectly sized. So this is a returnless system?

I am a little surprised that you set the final tune to be only a few WHP below the knock threshold on a motor with no knock sensors. Doesn't leave much room for dealing with off normal situations where the engine may be hotter. Did you tune for regular gasoline or awesome CA 91?

Chris can comment better. All pulls were on CA 91 octane, Chris did multiple hard pulls to make sure the engine was heat soaked and had one person listening at the engine for knocking and I was at the back tail pipe looking for any grey smoke. I believe Chris also installs a sensor that listens for knock as well. One thing he takes into account is how the vehicle is used, loaded down with gear, driving in the summer to go wheeling. He was conservative and aired on the side of caution.

[maxbraketorque]

Sounds good.

[hexdmy]

Originally Posted by maxbraketorque

Pretty interesting to see that fuel pressure begins to drop off just shortly after the stroker motor power exceeds the factory power level. The factory fuel pump is just perfectly sized. So this is a returnless system?

I am a little surprised that you set the final tune to be only a few WHP below the knock threshold on a motor with no knock sensors. Doesn't leave much room for dealing with off normal situations where the engine may be hotter. Did you tune for regular gasoline or awesome CA 91?

This engine was not as knock prone as many Jeep stroker engines tend to be. If it was, I would have backed off the timing a bit more to leave some extra margin. Final timing values were not much more than stock, that’s all this engine needs. I've worked with other stroker engines that even on 91, will knock with stock timing, in some of those cases you wind up running less than what the engine needs to get near MBT which is not ideal. Finally, I don’t “zero out” the AIT or CLT timing modifier tables like some others do, those tables allow for additional protection via reduced ignition timing at high temperatures. Thanks for your concern but I don't wish to engage in any further banter on the topic of ignition timing on this thread.

[maxbraketorque]

Originally Posted by hexdmy

This engine was not as knock prone as many Jeep stroker engines tend to be. If it was, I would have backed off the timing a bit more to leave some extra margin. Final timing values were not much more than stock, that’s all this engine needs. I've worked with other stroker engines that even on 91, will knock with stock timing, in some of those cases you wind up running less than what the engine needs to get near MBT which is not ideal. Finally, I don’t “zero out” the AIT or CLT timing modifier tables like some others do, those tables allow for additional protection via reduced ignition timing at high temperatures. Thanks for your concern but I don't wish to engage in any further banter on the topic of ignition timing on this thread.

Sounds like you got it covered.

[CMNCHE]

How much did this 80 RWHP cost? To me this doesnt seem very cost effective.

[-PigPen-]

Originally Posted by hexdmy

Here is the dyno data to review, I've included delta hp/tq data as well as some ecu data: intake air temp, coolant temp, injector pulse width, injector duty cycle, vss, measured lambda, commanded lambda, manifold pressure.

I tried to keep coolant and intake air temperatures consistent run to tun since the power numbers vary considerable with engine temps.







- Chris

Is there any data on the stroker output prior to the tune? It would be interesting to see how much power is left on the table without getting a tune.