Does anyone know if you change the ignition timing from the original 10 degrees BTDC to something like 14 or 16 BTDC, will it also change the fuel injector timing as well? Just wondering since I was "experimenting" this weekend with my truck, 94 351W/E4OD. Since I put on the 2.5" duals and headers, I feel I lost a little low end torque, but gained a "load" of mid-range power (perfect for towing) and was wanting to get back some off idle torque. I figured since the engine runs cooler now with no cats now, I can advance the stock timing. For those wondering, yes, I'm leaving it at 16 degrees BTDC. I've got most of the throttle feel back when I take off, not sure how she'll do towing when it gets warm this summer, it'll be another "experiment".

 

Yes, the injector timing changes as well.

 

going with a larger dual exhaust and not doing anything to the motor you will loose top end due to the lack of back pressure that helps get that lil xtra umph out of the motor: on the other hand it does have a dermastic inprovement on low to mid range HP and Torque which is why every one and there mother want's to put on a set of 3 in pipes and flowmasters that and it just sounds faster then it acctualy helps unless you have that 500 BHP motor that needs that much room to breath!

 

hmm, seems I actually gained top end a bit here, but lost a little lower end

 

Flow velocity is what helps low end torque, not backpressure. You never want backpressure.

 

make shure you remove the spout connector before setting the timing

 

I'm a little confussed. "nothing new"

but do ya set the base timing at 10 or 13 ?

I changed mine and it seemed like the engine went way down from what it was idleing at.

It seemed to go back up after reinserting the spout.....

Thanks

 

base is 10 BTDC

 

Base timing is at 10 BTDC.
Oh yea, I remember to take out the SPOUT, putting it back in...haha, now that's a different story, thanks for the reminder

I put the base timing at 16 degrees BTDC instead of 10, its a common thing at the shop here to put it at about 12. If you're not sure of the symptoms of what "might" happen if you advance the base timing, I'd recommend leaving it alone.
What usually happens is the more you advance the timing the better the torque at idle, but once again, becareful...if too much it'll not run right, wreck your engine, and a whole slough of other not good stuff. The theory is to advance the time the spark goes off, increasing the cylinder pressure just at TDC, thereby giving you a bit more torque off idle, a lot of things come into play though, spark knock and preignition are most prevalent if you use a low grade fuel, when you have high engine/incoming air temperatures, which is right now how, since it's only 25 F outside, I get away with the 16 degrees BTDC, so I'm not sure how the truck will like towing. That's why the factory most likely, uses 10 degrees, it's a compensation for different fuels, driving styles and scenarios.

I wasn't sure if the ignition timing affected the fuel injector timing, I was pretty sure it did, but I like to know it, so I know what to look for, should something come up.

 

what are you going to run for fuels 89 or 93 on the 16 deg.

 

Honestly, it's running on 87 octane as of now.

FWIW: It's got a really free breathing exhaust, no cats, headers, 2.5" duals, with glass packs. I've blocked the EGR completely with a custom block off plate, I really believe these are helping the engine, by keeping it cooler, even though the EGR might help with preignition, I've always had good luck, when it's disabled, I tend to get better gas milage, just my notion though, I'm not stating it as a must do modification.

Right now, I use my truck as a daily driver, 28 miles one way to work and a little bit of tooling around between places. Combined driving is about 13.8 mpg with about 15.8 -16.1 mpg highway driving, which I think is fairly decent. Like I stated, it's got a bit of the torque back that it had before now, and so far so good, I'm waiting for it to warm up and I'll try towing with it. I will have the timing light and tools on me, should the timing need to be changed. Overall, I'm pleased with the throttle response it did give so far.