Car now idles in gear, but surges

[webb1624]

I have been working on my tune and got it to idle in gear somewhat. The problem now is it wants to surge really bad in gear. Its like it wants to surge forward with the lope of the cam. The engine idles its best the lower I put the base timing. I am down to 10 degrees. It actually ran at 5 degrees but throttle response wasn't as good. I played with the timing table and fuel table but can't get rid of this surging in gear issue. Checked all vacuum lines and even unhooked them (all but fuel regulator and map sensor)to eliminate a vacuum leak. I will get a data log of car running in and out of gear this weekend.

Anybody have any suggestions as to which direction to go ?


1998 Ford Explorer block 347 ci
AFR 185 heads
Holley Systemax intake
Ed Curtis cam
Mac 1 3/4 shorty headers
75 mm TB
42 lb/hr Bosch injectors
Ford Explorer ign coils
MS3 w/ MS3X expansion V3.57
LC 2 wideband (2)
4R70W with Baumann Opti-Shift controller
Precision Industries lock-up convertor 2800-3000 stall

[slow_hemi6]

Are you having to really hold it with the brake? If that is the case I would be questioning what the trans is doing. 2800-3000 converter should be unloading the driveline a fair bit. What you are describing sounds like a big cam, stock stall scenario. It's not locking up the converter or something silly like that? Otherwise you need to have a look at the bins for VE and Ignition timing that are being used during the surge and make sure the same value for VE and timing are in all those bins and the ones immediately around it. See if that helps improve the surge.

[webb1624]

Yes, I really have to hold it with the brakes. My first thought was convertor, but 2800-3000 should be good. But who's to say that's what the convertor really is. That's what Precision Industries said it should stall at with my engine combo. I'm trying to eliminate everything else before pulling the convertor out.
I looked at the Opti-Shift on my laptop and its not showing the convertor locking when going into gear. I have also watched the cells for timing and fuel and they don't really move when going into gear.

[slow_hemi6]

Flash stall rating does not indicate how loose the converter is at idle though. Did you order the converter from precision and did you tell them the cam specs you are using? Can you take a datalog of transitioning from out of gear to in gear?

[webb1624]

I ordered it straight from Precision. They took all my engine specs, trans, and rear gear info. I'm going to get some datalogs this afternoon and post tonight.

[webb1624]

I played around with the car some this afternoon. It didn't matter what I did, the car would still surge when put in gear. I locked the timing at 10,15,20,25 and 30 and adjusted fuel each time and it made no difference. I went from 12 afr to 15 afr and it still wouldn't act right. I have a datalog of what the car is doing. You can see the idle is fairly stable until I put it in gear, then you can see the rpms start going up and down and then the idle stabilizes again at the end when I put it back in park.

I've had several race cars over the last 25 years and none have ever acted like this. They have all been carbureted and had a convertor with a good bit of stall in them. My last car had a small block with a HUGE cam and convertor was 3600-3800 and it was smooth as silk idling in gear. With this being a mild street car build, my experiences make me lean towards the convertor. Other people are saying its the tune. Maybe I'm missing something, but I have changed the tune enough that I think I would have found something that makes it idle in gear better than it does.

Any ideas ???

Thanks

[Matt Cramer]

I would try adjusting the timing a bit and see if you can stabilize it that way. You may need to add a bit more fuel as well due to the large cam plus bank to bank fueling. This often means you have significant intake reversion and this can have some cylinders run lean at idle.

[webb1624]

Matt, I have been all over the place with the timing. From 10 degrees to 30 degrees. And everytime I adjusted my fuel as well to keep the afr in check. I even tried going a little leaner and a little richer. Nothing I do seems to make a difference. If I raise the rpms to 1100 at idle it doesn't surge much at all when in gear. But I'm thinking this engine should idle at 850 in and out of gear. I haven't tried closed loop and use the IAC to adjust idle when in gear. Is that an option in this situation?

[slow_hemi6]

What is the duration and overlap on that cam of yours? Idle vacuum is pretty poor in the logs.

[Matt Cramer]

I would recommend abandoning the goal of keeping the idle AFR in check and just adjust the fueling so that the idle quality is better. Let the AFR fall wherever it falls with a good idle. Tuning the idle AFR when you have a big cam - lots of reversion, possible misfires, etc - is chasing your tail.

[jamies]

have you driven the car at all?

[rrrobert]

12.5 :1 ticokver mixture ,

a damper on the map signal ,

9 box field around tickover rpm all the same for timing.

i notice the mixture is varying with the oscillation in rpm .

maybe it needs to tickover a little higher .

[jamies]

drive the car and see what the converter feels like, you shouldnt have to be on the brake hard at idle, if its pulling through the brake at idle then id be looking at the converter

[webb1624]

Cam is from Ed Curtis @ FlowTech Inductions. Duration is 230 intake, 242 exhaust. Lobe separation 111. Intake centerline 108. I have only driven the car around my property just to verify the operation of the transmission. I haven't been on the street yet. It is definitely pulling through the brake. If I don't apply the brake the car will start moving in gear and it surges while doing so. I can get a fairly smooth idle, just can't get it smooth in any gear.

[webb1624]

Taking Matt's advice I adjusted the fuel table today to see what would happen. I went all the way up to 85% fuel load on the VE table and also moved timing around and it made no difference. One thing I did notice is that it does it worse in reverse than in forward. This happens with any tune I use.

I was looking back at my cam notes and I had to retard the cam 4 degrees to get it on the 108 centerline the cam card suggested. Intake opens @ 8*, closes *42.5. Exhaust opens @ 56*, closes @ 6.5*. Does this look like a cam issue ? Would this cam cause the reversion issues I'm reading about ?