Engine and Transmission Tech

Hey guys,

When wiring V8 fuel injectors in a 2 bank configuration, would it make sense to bank the 4 outer cylinders together and the 4 inner cylinders together? My idea is to allow for a slight richening of the mixture of the outer 4 cylinders, (assuming the outermost cylinders might run a bit leaner), without affecting the AFR of the inner most cylinders. My thoughts are based on the MS II's dual injector drivers. I remember reading somewhere that Rover GEMS EFI tend to run lean in some cylinders which presents a more serious issue when running boost. Is my thinking here flawed or feasable?

Thanks,
Mike

You can do that Mike. Check with Bill Jacobson as I think that's what he did to counter a lean imbalance in his intake manifold using the dual tables feature. I suspect it'd be a bit more tedious to tune but I haven't tried it. Can't you adjust the stack height to counteract that problem? I thought that was the usual solution with an EFI package.

You can also group them by side which can work well with the O2 sensors, or inside on one bank with outside on the other which is more consistent with dual plane intake design and may arguably even out flow in the fuel rail, though I'd consider that a minor consideration.

Jim

Jim is correct, I do have the inner cylinders on table 2, outers on table 1. (#1 cylinder = #1 table, so it's easy for me to remember)
You can even wire them up 5 or 6 cylinders on one table and 3 or 2 on the other. MSII can run up to 6 injectors on one bank/table. I tried it for the heck of it and it does indeed work!
What I did was tune the motor on one table, all injectors commanded the same. Then checked the plugs, the inners were slightly leaner which is common on a open plenum manifolds.(with port fuel injection)
On a ported fuel injection system, the inner cylinders can run leaner. This is because the "air supply" for the inner cylinders is closer to the source. While the fuel supply is at the intake port and fairly constant for each cylinder. So basiclly the inners are getting more air then the outer cylinders.
The opposite would be true on a carbed or TBI engine. Where the fuel supply is at the center of the manifold and therefore closer to the center ports. Because fuel dosn't move as well as air, the inners can draw more fuel then the outer cylinders, due to the shorter distance the fuel has to travel.
When I tune the motor, I use table 1 for my VE table base-line adjustments. Then simply import table 1 data into table 2. From there I use the table shift function to bump up all of table 2 a couple percentage points or so to richen it. Then burn it to the ECU and then save tables 1 and 2 in Mega-squirt. Just takes a couple of key strokes and is fast and easy to do.
What takes some time is the initial tune, reading the plugs, figuring out which cylinders are leaner then others. Once you know that, then you can make your VE adjustments and just keep the same table 1 to table 2 spread.
If you have a daul plane manifold, you may want to start with injectors wired by firing order. Then tune it with a single table and check your plugs. It's easy enough in most cases to swap the injector wiring around latter if you need to. I have seperate wire colors for each injector run all the way up to the ECU. Makes it easier to swap your curcuits around if need be.
Very few intake manifolds have perfect cylinder distrubution, and the balance can change at different RPMs for a given manifold. But it is handy to be able to have the ability to tune the fuel balance to the manifold!

Bill

Jim Blackwood:
You bought one of my ECU chips at the meeting in Durham?? You asked what the fueling rpm limit was, and I later remembered it was 8000rpm. Obviously you should not rev the engine higher than 6000 unless it is built to do this.

Interesting subject that the 3-4-5-6 cylinders would get more air than 1-2-7-8 cylinders. Have not seriously considered this before. I have considered the actual length of the 8 runners on the EFI type intakes. Will post the cc's per runner later when I find my notes.

Just glancing at the CUX type of intake manifold, you can see that the 4 ram tubes in the middle are an inch or more higher than the outer cylinders. Even if overall the runners were the same length, the extra ram tube length for the middle cylinders might reduce some of the airflow.

I assumed the CUX type plenum roof is also arched so the height above the ram tubes is similar across the 8 cylinders. I also assumed this spacing above the tubes was for reflecting "sound waves" back down the tubes. Will measure the space above each tube to see how consistent it is.

Randall Smith

Thanks guys!!! I knew I could count on you steering me in the right direction. I appreciate the amount of detail in your answers as well. I guess I got the EFI vs carb intakes backwards regarding which cylinders might be lean. Your explanation makes total sense. I will be running the stock 1998 Range Rover 4.0 intake and plenum. The upper plenum is a 4.6, not sure its any different from the 4.0 but stock factory equipment just the same. I'll likely stay with the stock EFI when it's time for boost as the configuration makes it easy to connect the ducting. I'm looking forward to getting the 4.0 up and running and having the availability of tuning with the Mega Squirt. I'm ready to design my harness and get started on it so I figured I should pose the original question.

THANKS AGAIN!!!
Mike

Randall, that wasn't me. But thanks for caring. Mike, best of luck with that setup, we're all here to help if you need it.

Jim

Mike

The GEMS type plenum was slightly more volumous than the CUX plenum and had a flat top. The intake manifold and ram tubes were the same.

Approx 10 years ago the Land Rovers that had the GEMS system had a horrible reputation for "sticking exhaust valves". The trucks were literally lined up around the dealerships to get head jobs with new "carbon cutter" exhuast valves.

This really made no sense to me. So I decided to find out what the real problem was. When I would ask people in other coutries about this, they did not know there was a problem. So the real problem was now found and then tested by inquiring the following on bulliten boards like this one: IS THERE ANYONE OUTSIDE OF THE USA HAVING A PROBLEM WITH STICKING EXHAUST VALVES?? The problem did not exist anywhere else.

The dealers were making a lot of money doing head jobs under warrenty, but eventually all the NAS computers were were reflashed and "sticking exhaust valves" (lean mixtures) are a rare occurance again.

I can not find the exact CCs of the intake manifold right now. But I did find my note that the OVERALL length of the 1-2-7-8 runners is actually longer then the 3-4-5-6 runners by mayby 1/2". The outside ones are longer even though the inside ones look longer.

I also CCed the intake runners in the cylinder heads. All of the cylinder head intake runners are exactly 100CCs.

Randall

Randall

Quote:

I can not find the exact CCs of the intake manifold right now. But I did find my note that the OVERALL length of the 1-2-7-8 runners is actually longer then the 3-4-5-6 runners by mayby 1/2". The outside ones are longer even though the inside ones look longer.

It's been awhile since I looked into this, but here are my runner measurements:

Quote:

The inside diameter of each trumpet is 3.81cm. The cross-sections of the runners in the cylinder heads are significantly smaller, but in the intake manifold the runners quickly transition up to round cross-sections of about 3.8cm diameter each. The average total length of all eight runners measured from intake valve to open plenum is about 38.75cm. (Runners 1 and 8 are approximately 41cm long. Runners 2 and 7 are approximately 39cm long. Runners 3 thru 6 are approximately 37.5cm long.)

ref: Service and Troubleshoot Rover 14CUX Electronic Fuel Injection, The British V8 Newsletter, Volume XV Issue 1

I wouldn't call these measurements exact. They'd be a lot more precise if I had cut the manifold and heads into sections.

WOW guys, that's alot of info! Very interesting... I had heard of the "sticking" problem before but had no idea it was a tuning issue. I hope to eliminate any mixture issues with the MS II and a lot of tweaks.

I always thought the inside runners on my old CUX intake setup were longer so I was surprised to know the outers are actually longer. I suspected the lower plenum on my GEMS flattop 4.0 was basically the same but guessed the trumpets were same height all across, haven't had the upper plenum off of it.

I love that Rover continued to develop and improve on the original 215's design for so many decades. I cannot think of an all around better V8 as compact, light weight and affordable with decent parts support plus it's just cool looking. I know they are not without their issues but to be able to buy an all aluminum V8 for such a reasonable price makes it very worthwhile to me.
I appreciate everyone's input and look forward to sharing the results of my little project with you!

I've been unraveling the stock underhood harness on the Ranger, identifying circuits and developing a strategy for the new composite harness. Along the way I will be tidying up a bit and streamlining for a cleaner than stock appearance.
Fortunately my Ranger is a base model so it has less wiring than it could've, still, it will benefit from some trimming down.
I'm planning to mount the Megasquirt II, the MS relay board and the EDIS-8 module under the dash to localize the components and simplify the installation and wiring plus tach hookup. I modified the factory coil pack mounting bracket to accept the pair of Ford quad units in place of the 4 Rover twin coils. They are barely noticeable and will make for a short wire run to the module.

I'll post up some pics when I have some of interest...
Mike



Edited 1 time(s). Last edit at 08/02/2009 06:08PM by Black P-38.