Multiport vs TBI, and DIS conversion.

[Canyonero]

My 3.4/3.1 multiport intake conversion has been moving at a very slow crawl. I had been running a 3.4 SFI intake with the 94 OBD 1.5 SFI ECU and I have been working on converting to the 3.1 Camaro/Firebird intake with a 1227727 MPFI ECU. (at the same time I have upgraded the cam with 1.6 ratio rockers)

The Trooper originally had the 2.8 with TBI, and I'm tempted to revert to the conventional TBI swap on my 3.4 for simplicity. I have a 1227747 TBI ECU that is a direct swap for the 1228062 that came with the Trooper and will provide better tuning support. Since I have the crank sensor I'd like to retain DIS, so I'd still have some originality to my project.

Think there will be a substantial performance hit from reverting to TBI? I do have an intake bored out for a 4.3L throttle body.

I certainly don't look forward to dropping my tank to get at the fuel pump again.

[geoffinbc]

I don't believe you will loose any power. Also you will not need to change your fuel pump. Keeping the DIS won't work since the timing will be way off and I don't think there is any way to correct it. A distributor works very well anyway so there is no sense not using it.

[Canyonero]

Remember, I have been running this engine with multiport. When I converted to multiport I installed a different fuel pump (from a 2.6L multiport Trooper) as I needed ~45psi at the fuel rail.

As for the DIS, why do you suppose new cars use DIS? Simpler, better spark, no moving parts... Just need to change the spark reference angle in the ECU to compensate for the difference in timing. I did this already when I ran my 3.4L with DIS off code from a 3.1L with a distributor. I figure my 3.4 block has a crank sensor, so why not use DIS. It IS better.

[Superdave]

DIS > Dizzy

[geoffinbc]

Remember, I have been running this engine with multiport. When I converted to multiport I installed a different fuel pump (from a 2.6L multiport Trooper) as I needed ~45psi at the fuel rail.

It does not matter. Pumps don't make pressure, they only make flow. Your new regulator in the TBI injector pod will regulate the proper pressure.

You can use DIS if you have a solution for the timing problem.

[robertisaar]

if its wiring issues, i might be of some help...

and since when does a 7747 have better support than a 7727? $A1 is more defined than $42...

[Canyonero]

Meant to say that the 7747 has better tuning support than the 8062 that the Trooper had, and the exact same wiring/pinout. I have run my stock 2.8L trooper on the 7747 with 4.3L code, didn't run perfect (and my O2 sensor was bad I think), but I drove it to town and back just fine. The 3.4L with a bored intake and closer VE to the 4.3L should run even better, but best with tuning of course.

The 7727 will be going on the shelf for a future multiport project.

[robertisaar]

i guess if you want to keep TBI, go for it. didn't know the 8062 and 7747 were interchangeable, but TBI isn't my area of interest either

so its just tuning issues for now?

[Canyonero]

Yeah, they're a direct swap.

I still have to pull the partially installed multiport setup and install my TBI manifold on the 3.4L, so a little more to do yet. I have all the parts on hand. I have another stock 2.8L TBI trooper, I've tested the 7747 ECU on that.

I want multiport, but the TBI is just so much easier. Everything fits as stock.

[Canyonero]

It's been quite a while since I've updated, but the TBI is back. Truck has still had chronic problems though. One of my new lifters is bad so I have a noticable tick. Comp mis-packaged one of my rockers, so I have one 1.52 ratio installed with my eleven 1.6 ratio (didn't notice when I installed them, noticed when I had the covers off troubleshooting my bum lifter).

The engine knocks and nothing I do with the timing seems to help. Here is the WinALDL table. All the knocks at low map and most above 3200 are from free-revving the engine when I got back to the garage. And this is after I've gone over the spark table three times and dropped 0.5 degrees where there were >10 knocks (using someones VEFixer spreadsheet). So I've dropped 1.5 degrees in some places (cruising speeds) and the knocking still persists. My timing advance is set to 10 degrees, which is what the manual says, and I've verified the initial spark advance being at 10 degrees in the BIN.



I'm going to convert to DIS during this downtime. I've pulled my DIS wiring out of one of my old harnesses and worked out the conversion on paper. Since I don't have A/C currently, I'm going to put the coils in the stock 3.4L location, on the power steering bracket. If I ever reinstall the A/C, I'll move the coils back where the current coil and dizzy are.







My plug wires look untidy because they are the set from when I was running DIS, the lengths aren't right for using with a dizzy.

[robertisaar]

you did remove all ALDL added spark, correct?

if not, it can cause issues like this.

[Canyonero]

Where do you do this, in the bin?

I have a Moates unit with a switch to enable/disable the 10k resistor. Using the 10k puts it into ALDL mode doesn't it? WinALDL was reading fine without the 10k, so I've been running it like that.

(edit: My BIN has Spark Added in ALDL Mode, 8.09 degrees)

[robertisaar]

zero that out and i bet MOST if not all of the knock goes away.

EDIT: http://60degreev6.com/forum/f121/tbi-headache-t44118

[Canyonero]

Oh, now I remember that conversation. I just disabled the 10k and assumed all was well. I'll try that.

[robertisaar]

Tricksy, the GM hobbitses is.