Howell EFI & Engine rebuild & correct cam

[Tbeach]

I have a 1991 Grand Wagoneer in California with 112,000 miles. Recently had the engine rebuilt, with some mild upgrades. Also upgraded to Howell EFI. The chosen cam is a Comp Cam XE 262H. Duration at .050" intake 218 exhaust 224.

Everything is together, idle is smooth, but there is a low end hesitation and it stalls every once in awhile. We have checked grounds, the alternator has been upgraded, and check all vacuum connections. With many hours researching this forum, I have come to the conclusion that the camshaft is the issue, specifically the duration of the cam. Howell recommends below 210 and 220, and I have also read on this forum to stay below 208 and 215.

So short of removing the cam and installing a new cam with the lower duration, are there any other workarounds?

Thanks in advance for your input.

[babywag]

tuning helps

[wiley-moeracing]

well thinking outside the box, what about creating a vacuum with an electric vacuum to a canister to the intake? may trick the computer into working better? might ry this with a race motor that was having issue during the norra race this year with the same issues?

[tgreese]

How about increasing the fuel pressure?

[wiley-moeracing]

That's not a bad idea either, just need to figure out how to fool the computer to make it work better

[Ristow]

drop in some rhoads lifters.

[babywag]

retune and disable closed loop would be better band aid

[wiley-moeracing]

unfortunate that you are having these problems, I will stick to my carbs till I can afford a good fuel injection system

[gpcl16]

I ran into similar issues when trying to get my Howell system to work with a non-stock cam. I'm assuming you have the CARB legal version since you're in California? If so, Howell will not adjust your tune, it's illegal for them to do it. That's my biggest gripe with the Howell kit, although it's really not their fault, just California laws. There is one CARB legal tune that Howell sells that supposedly runs a bone stock engine. Make sure your fuel lines are not kinked and your return is not restricted. Assuming your engine is mechanically solid, and your ignition system is all good, you will need to re-tune it yourself or bring it to someone who can do it for you.

EGR can also wreak havoc with the Howell system since it is controlled by the stock Jeep Thermal Vacuum switch rather than the TBI computer as GM intended. I have no idea why Howell didn't include an EGR solenoid with their kit, that's my 2nd biggest gripe. EGR can make a massive difference in the required fuel so it can throw your fuel ratios way off under some circumstances. Fuel trims can only compensate so much in closed loop, and your open loop fuel ratios could potentially be way off.

Try plugging the EGR vacuum and see if your problems. You can also add a vacuum delay valve or a smaller orifice washer to your EGR as well.

Ideally I would buy a GM EGR solenoid and wire it in to your computer, and re-tune for it. Or you can run without it and call it good. Reconnect it when it's time for smog check. Personally, I feel the EGR provides some fuel savings under light throttle conditions so I recommend keeping it if it is tuned properly for it.

[gpcl16]

drop in some rhoads lifters.

I just did some research on these but found limited info. How do they work? They increase vacuum at idle?

[Ristow]

They are a bleed down lifter, at low rpm the inner piston of the lifter bleeds down, thereby reducing the actual lift duration of the cam. As Ron?s rise the bleed off reduces to nil.

[PlasticBoob]

If this was happening on my Jeep, I'd say that I really don't think the cam is the issue at all. I think it's your accel enrichment shot or possibly the off-idle cells in the fuel map (high kPA).

I don't know anything about the Howell system though - two questions.

1) Are you able to capture any logs at all to see exactly what is going on the millisecond before it stalls?

2) How tunable is it? Some people with BMW N54s will run a 450hp non-California ethanol tune, and then re-flash over to the stock tune when it's time to smog it. This is of course the most illegal thing you can do in California, and of course it is not recommended to break California law, even if you're the Feds.

Bear with me, this is very hard to explain without a video or photos...

On my system, I have created two different maps over the years: one of them has a buttery smooth idle, and the other makes it sound kind of like a mean lumpy race engine (it's not, lol - all for show, folks).

I had to really change things around to get the lumpy map right, and that included "zooming in" and making the cells of the lumpy idle area relatively lean (nothing dangerous). Of course, this created a hesitation that I had to compensate for. I did this by adding a second column for any fueling that happens above 835rpm. Everything in this column was richened back up. Columns in the table below 835rpm had a nice big rectangular area of "lean" cells to produce the lumpy idle.

Then, I had to adjust my "accelerator pump shot" in the software. On my system, you can use MAP, or TPS, or a combination of the two to set the shot. I am using only TPS (due to the lumpy cam), but I enrichened only the slow tip-in pulsewidth bin just a bit, and now I can seamlessly transition from a lumpy idle to extremely smooth operation above 835rpm.

I have the Comp Cams XE 256H, which is a smaller cam, but still has intake duration of 212 and exhaust of 218. That's borderline according to what you posted. It also has a lobe separation angle of 110*, which again was not recommended at all for fuel injection - but everything is working great! Also, I'm not running any EGR.


Here's an early "beta test" video of the effect I'm trying to perfect. Yes, I installed and have to mess with a computer to get the same effect as a carb. It's still warming up here:

https://youtu.be/L6U_oQmYkh0

Great trick for cruising down to the car hop at idle in gear.


And here's a video from earlier in the process after it's warmed up with a higher idle:

https://www.youtube.com/watch?v=uXDlNSirmOE

You can see the VE (fuel, really) table here. The transition area is between (835, 75) and (900, 45). The high resolution lumpy idle area is between (600, 75) and (835, 40). The off-idle area you can see as the tracer moves. Can't wait until I upgrade to the newer version that lets me have a 16x16 table!

Also, pay no attention to the crazy lean idle AFR; oxygen sensors don't like lumpy cams and think it's the end of the world.


Feel free to skip this block of text
[I just need to fine tune a few things...I can't get a perfectly steady lumpiness, because I don't have a 1:1 tach signal, and am using some noise filtering, as well as using a caveman distributor to control the spark and tach signal. You can hear the disruptions to the idle as the computer over or underfuels because it doesn't know exactly how many spark events are occurring. This is not a problem on the "smooth idle" map because this cam is supposed to idle slightly rich (if tuned using the vacuum gauge method) and so there is always a little extra fuel around in the runners for a cylinder to suck up to compensate for the tachometer averaging/lag algorithm.]

But I digress. Maybe you can try something like what I did to dial in your tune.

[babywag]

The Howell system “tune” is very similar to a stock GM tune.
They changed VERY little.
The fuel map is ok-ish for a stock cam.
When a larger cam is used, and vacuum decreases, the whole map is now way off. The fuel map is based on RPM vs. MAP(vacuum), a big cam & lumpy idle it will bounce around on different cells of fuel map.
The fuel map needs to be correct before changing things like acceleration enrichment.

Even a stock engine/cam benefits from a tune. Regardless of what people say there is no such thing as a turn key system. The ecm can only “learn” & adjust so much. If you have a bad tune it’ll never run “right”.
If you want it to run better/correctly you gotta tune these.

[Tbeach]

I appreciate everyone's input and advice. My mechanic is in the process of changing out the cam (milder) then will retune. Howell did send us a new chip for the more aggressive cam, but still not perfect. And yes, we are keeping everything legal since there are limitations here in California.

[babywag]

I appreciate everyone's input and advice. My mechanic is in the process of changing out the cam (milder) then will retune. Howell did send us a new chip for the more aggressive cam, but still not perfect. And yes, we are keeping everything legal since there are limitations here in California.

Be aware you can do a stealth timing control setup.
Gut Duraspark module and hide 7-pin module inside.
Lock out advance in distributor. Add correct wiring and change .bin to do timing control.
My ?90 is like that, been smogged many times, virtually undetectable.