XDi ignition systems users
 

Would like to pick your brains a bit. I am using the XDi system on my twin plug 3.3SS engine. As a starting point, I have the 4 timing dials set at:
1) 10 degrees
2) 24 degrees
3) -2 degrees
4) 5,000 rpms

With #1 being the initial timing, #2 is max advance, #3 (adjustable) backs off the timing -2 degrees on top end and #4 is the max rpm cutout setting. Compression is 10:1 and cams are the 964 units. Any real world experience/suggestions on the timing?

Thanks,

That will be fine.

5k RPM Max Cutout?
 

If Steve says the settings are fine - I'm sure they are fine.

Meanwhile I'm planning to go with XDi single plug on my 3.2L rebuild. Appreciate if you could explain the 5k RPM cut out. Is that the RPM limiter (doesn't let you throttle up higher than 5K?).

If so, why such a low RPM cutout (I planned on limiting mine to ~6,500 RPM with only bottom end mod being ARP rod bolts).

Thanks, been following your rebuild thread - great stuff.

Best of luck,

Gordo

I'm also doing this with single plug on stock 3.2. Will also try the vacuum (pressure) sensor piece. I'm thinking 36 BTDC total advance at 3K RPM.

RPM Limit
 

I've got it set at 5k just for the break in period. After that, it goes to 7K! The upper limit on the unit is 15K!

Single vs Dual Plug timing......
 

Sounds like your numbers will be correct for a single plug engine. One of the advantages of having the Dual Plugs is that the max timing advance with dual plugs is less (22 - 24 degrees). This supposedly will let the engine run cooler and be less sensitive to knock. One reason why I decided to go with the XDi system is that the timing is just about infinitely adjustable by simply turning the 4 knobs. One thing that I did when installing the timing sensor on my engine was to set the gap and then put a small hose clamp on the (round) sensor. That way, I can remove and re-install it without having to measure the gap which is somewhat difficult to do with the engine in the chassis. Good luck with your project.

Make sure to take note of the relative position of the crank sensor to the toothed wheel. If the crank sensor is not at the trailing edge of the 11th tooth, you need to adjust your base/dial settings accordingly. Being off by one tooth = 6 degrees!!! (360/60 teeth = 6 degrees per tooth). Don't assume the crank sensor bracket automatically "zeroes" you at TDC.

Even if you happened to be spot on with your correction relative to tooth #11, you MUST check your timing with a voltmeter or timing light. DO NOT rely on the dials to be accurate.

A handy tool to use to set up your ignition is this trigger simulator

Fifty Eight Tooth (60-2) Wheel Simulator - Electromotive Engine Controls

It fires the ignition w/out having to run the engine. In the case of the simulator, you need to confirm the actual timing setting by reading it with a digital voltmeter

Checking timing
 

Yes, something else to do before driving the car. I think the battery in my digital volt/ohm meter is dead so will have to get a replacement battery. This is on my short list of TTD. When I was assembling the engine, I set it all up very carefully and counted the teeth on the trigger wheel. I believe that it is "right on" the correct tooth.

XDi has knock control, too. Works well with 993 knock bridges.

XDi Timing Check
 

Got new batteries for the digital VOM. Did a timing check on the XDi system. I must have gotten it put together correctly as the VOM matched the reading on the dials
+- 1 degree! One more "thing to do" off the check list!

Must have XDi2 (squared) to get knock control. Basic XDi not capable of knock unless piggybacked with another controller

I ran my 2.7 race motor (46s, big cams, nominal 10.3/1 Mahle race pistons, crankfire twin plug) with:
0 static
12 at 1,000 for 12
14 at 3,000 for 26
2 at 8,000 for 28.

Worked fine.

Once you have your motor broken in, take the car to a chassis dyno and get a torque curve. Use the torque curve and your transmission gearing (you don't need tire diameter or R&P for this, but can add them in) to develop "thrust" curves at 500 rpm intervals for each gear. Where these curves cross (all will except first for stock type gearing) is where you should be upshifting, as the delivered rear wheel thrust will be equal in the "old" gear and the new, higher, gear. Those are the optimum shift points. You can do this with a pencil and graph paper, or make a spread sheet so you can easily see how changing gears or torque curves will affect things, etc.

I had been shifting at 8,000 rpm. The motor mechanically will take this well enough - may shorten valve spring life, but then overrevs which don't bend any valves can also shorten spring life. But with a torque curve I found 7,600 was the place to shift. Sort of win/win, doing it right and gaining acceleration while reducing strain.

Do you think the 964 crank will produce a torque curve low enough that your optimum is below 7,000?

Unless you are using stock rod bolts, I'd think you might up your limit if you autocross or do DEs and the optimum is over 7.

Fred - looked at your main posting on this motor. CIS intake. Ah, maybe 7,000 is as high as you would ever need to go.

Does XDI (I used the original Electromotive crankfire system, and now have the Tec3R, but don't have XDI memorized) support shift lights? Soft rev limiting? Lights are neat to have, especially if for whatever reason your tach quits working occasionally when on a track. No real problem in the shorter bits where you can just upshift by where you always do and not bother with looking at anything other than the track, but those upshifts on long and somewhat featureless straights (think backstraight at Sebring) work better when you have an idea of engine speed.

XDi .............
 

The XDi does use soft rev limiting, but not a shift light. It also can use/support an external rev limiter and a couple of other features related to boost that I did not need. The basic wiring for the XDi is pretty simple, with getting the two small harnesses that feed the DFUs plugged into the master harness being the most difficult part. Other than that, there are 4 wires plus a ground wire that need to be connected. The tach feed wire from the XDi plugged directly into the wire to the tach without any adapters. The only complication that I had was due to using the CIS system with the DFUs mounted on the shelf behind it which hides the right side DFU. When lifting the engine into place, I got it within about 6" of being in and then plugged in the bottom spark plug wires. If necessary, I can pull the CIS boot and see to work on the plug wires. Thanks for your thoughts on this "issue" with my new engine!

Help with XDi...Just installed my system...Fires right up but I have to shut it off because it goes wide open(didn't hit the rev limiter). Seems like a vacuum problem. I used golf tees in the two small lines from the old distributer. Anyone have a similar problem???

Timing
 

Is your system single or twin plug? What do you have the timing dials set at? Also, check to make certain the plate that lifts with an open throttle is not stuck open. I used the 10/24/-2 settings (twin plug) and my engine ran quite well. Also, check to make certain that your sensor is reading the proper tooth on the crankshaft degree wheel.

Thanks...I used the settings that Clewett Eng recommended. It.s a single plug. .050 air gap, Initiall timing 12 deg, 3000rs 21 deg, 5000 red line till break in. Degree wheel is pre set for 911 by the pin. Thanks I think the plate might be the culprit might be the plate.

XDi
 

Be sure to check your timing event with a timing light. and if possible watch the timing while doing a dyno pull to be sure.
Mike Bruns

Sticking throttle pedal
 

Ever since I lowered my motor to put on the Clewett crank pulley I have a sticking throttle pedal. Could I have damaged the linkage when I lowered the motor?

If you lowered the engine a large distance, sure you could have bent the throttle rod that comes out of the car chassis.

Take off the throttle rod that connects to the bell crank on the side of the transmission. It's a ball socket that you just pop off by leveraging with a 10mm open end wrench. Once disconnected, pull on the rod that goes into the car and see if you feel any hang-ups