DTT or Crane?

[BLB350]

Mike, I must run my 2000 FXD 110" 9.9 Static CR (9.1 corrected for intake closing) on the #4 SE curve to prevent detonation at 2000 rpm, but runs much better on curve #2 from 3000 rpm on up. Because of this, I am considering an aftermarket ignition that is programmable. My #1 concern is reliability, and I would like to maintain the ability to recover trouble codes. What would you recommend to me, a Daytona or a Crane, or??

[Mike]

I could be wrong, but I think the DTT is the only one that has DTC capability or it has it's own software add on package that does data monitor for DTC diagnostics. Again, I'd have to contact each or do some research to confirm. I do know the Dyna system does not support DTC's.
Mike

[BLB350]

Mike, I got the DTT & it sure is neat to be able to burn my own timing curve into the ECM! However, I still have some funny business going on that I don't understand. I programmed in really slow timing for 0-1500 rpm (0-8 BTDC), 18 BTDC at 2000 rpm and then ramping up to 32 or so by 3000 rpm. (remember that I have a 9.1 CCR.) When I am going down the highway at low rpm, say, 60 mph in 6th gear (about 2000 rpm) and crack the throttle open, there is no detonation all the way up the rpm band. When I am sitting idling, and blip the throttle (not fast), it detonates. Since I am running 2 front heads and have the map sensor on only the front cylinder, I reasoned that maybe the vacuum is going away too slowly causing this detonation. So I back off all advance in the lower rpms with rising vacuum (use the same WOT timing at any vacuum). I only increase the advance with rising vacuum (for gas mileage) at 2500 rpm and greater. While this has helped immensly over the SE adjustable ignition I still continue to have a detonation problem off of idle at NO LOAD conditions?!? Another thing to note; the engine sounds really retarded at low rpm, making that loud "blat" sound instead of the crisper sound at higher rpm. I am also running rich pilot jets (#30) with about 1 turn out on the air screws of my HSR45's. Got any ideas?

[Mike]

I would put a little more idle timing in around 22-25. The minor ping off idle may be the MAP sensor being too slow to respond or maybe a little more accelerator pump (or ealier) is needed. Does not sound like a real problem fi you cannot completely cure so long as it stays right off idle.

BTW, got the "pieces" in the mail. Thank you VERY much, looking for a ginny pig to try them on and anxiuos to do so. It may take some time. I think you may be on to something.
Mike

[BLB350]

Mike, I talked with DTT and they indicated that 2 intake manifolds will not work with the type ignitions run on TC's. The ECM samples the MAP sensor reading at BDC in the intake stroke for both cylinders. Since my MAP sensor is only on front intake manifold, it is getting a "bad" reading when it takes a sample reading for the rear cylinder. I plotted it out and the rear cylinder sample is being taken just before the exhaust valve opens on the power stroke of the front cylinder. DTT's only suggestion was to connect both intake manifolds together with a 1" hose, and mounting the MAP sensor midpoint in the hose. You had mentioned on previous threas about connecting the intake manifolds together. Could you restate what size lines you have seen (Baisley?) please?

[Mike]

We've used just small vacume hose that fits whatever "T" or "Y" we're using. Tha small the hose (and fitting) the morre dampened the signal. Of course the more dampened the slower the response, so some experimenting with hose and ftg sizes may be required to get the right balance.
Mike