Red0ktober

Hello all, I have a 1990 Isuzu Trooper which came from the factory with the GM 2.8L w/ TBI. I've swapped that for the 3.4L from a '94 Firebird with a Crane H260-2 Cam, Comp 1.6 ratio roller rockers, Comp springs, bored intake manifold with the TB and injectors from 4.3L V6. Exhaust is stock down to the y-pipe, 2.5" high-flow magnaflow cat and 3" cat-back with a flowmaster (loud!).

I've done little with the intake, just have the lid flipped on the filter housing with a standard 10" round filter. I was thinking of putting on a TBI spacer and an open-element filter, but I think that will get dirty quick in a 4x4.

I have the stock 1228062 and a 1227747, both with ZIF sockets installed. I have TunerPro RT and the Moates APU1 for burning, datalogging, realtime, etc.

The truck is my "daily driver" (well, I don't drive to work, so more like a few times a week driver...) so fair gas mileage would a plus, but I've had the truck eight years and I know the mileage from a 3800lb vehicle shaped like a shoebox can only be so good.

The truck has some serious low-end grunt now, no replacement for displacement! I'm much lighter on the throttle to get the truck moving. It doesn't do bad, but I guess I was expecting more from the top end. I knew from the beginning that I would be tuning on this.

Actually, this isn't the beginning. I was running multiport on the 3.4L in this truck and had big plans in that regard. But I bit off more than I could chew when I swapped the cam and was going to change out the intake, ECU, and most everything else on the top end for better flow and tunability. I had a 1227727 ECU and harness made up and everything. But I kept running into fitment issues and finally got frustrated and dusted off all the TBI components to get the truck back on the road before winter (and it is, so I don't regret that decision). I might bring the multiport back someday, but I'm going to get everything prepped on an engine stand first. It was just too much trouble doing all that in the engine bay.

Anyway, it's TBI for now. It seemed to run decent off the 4.3L's '7747 ECU when I loaded it with code for a manual tranny, adjusted the BPC for my engine, and did a little VE adjusting. But I was getting some serious pinging, ended up bringing the timing back where I was having the highest knock counts which makes me more comfortable driving it. Still hear it pinging sometimes, but not consistently. I've swapped over to the '8062 ECU as I work with other Troopers and I want my mods to work on a friends truck who is doing similar mods. The '8062 doesn't respond the same to changing the BPC, so I left it at 166 (which actually figures to be the value for a 3.1L, not the 2.8L...). So I've left the BPC alone, made a couple passes on the VE (but more could be done there), and tweaked the spark table so it doesn't ping.

This is my first delve into tuning, maybe I'm not doing things in the right order. So I'm looking for advice. I've been going through some of the stickes here, but maybe someone here wouldn't mind helping me work through this too.

Fast355

iTrader: (2)

I ran a TBI swapped 3.1 with a Crane 272 came in my S10 Jimmy. I was running a 4L60E and a 427 PCM from a 1994 TBI 4.3/4L60E Astro van. I was doing my own tuning and got it running VERY well.

Red0ktober

The knocking is bothering me. I never noticed it knocking when I had the SFI setup on there (w/ DIS). The dizzy advance is supposed to be 10 degrees, which is where it is... Verified that the Initial Advance is correct in the BIN. Truck seems to run pretty good otherwise...

I'm a little confused about what I should do with the BPC. I calculated the value for the 3.4L with 46# injectors. In the process of calculating that value, I also calculated the stock values for the 2.8L w/ 36#, the 3.1L w/ 36#, and the 4.3L w/ 46#. I found out what the BPC is in the stock Trooper 2.8L ECU, 166. Should be 150. 166 is the value for the 3.1L.

So should I ignore the fact that it's "wrong" in the oem chip, go ahead and change it to 143?

BPC = 1461.5 * (cyl size / gm/s of fuel)
BPC = 1461.5 * (0.567 / 5.796) = 142.97 (3.4 w/ 46#hr)
BPC = 1461.5 * (0.716 / 5.796) = 180.54 (4.3 w/ 46#hr)
BPC = 1461.5 * (0.467 / 4.536) = 150.47 (2.8 w/ 36#hr)
BPC = 1461.5 * (0.516 / 4.536) = 166.27 (3.1 w/ 36#hr)

Red0ktober

I went back to the stock tune, changed the BPC and did a drive to ballpark my VE. Just had to search for the idle a bit on the initial start, but it ran way better than I thought it would (I swear I tried that before...).

I'll take it for a drive tomorrow for a second pass on the VE.

Something interesting, there are no values in the VE adder table... Curious...

Red0ktober

After the second pass on the VE, the thing pings like crazy now. What the hell?! Did I do something wrong, or do I need to bring my timing back?

(actually, it was the first pass, I apparently didn't save the table the first time so I was at the same starting point.)

Red0ktober

Isn't it great when a google search brings you back to a thread you yourself started... It feels like much longer ago though...

So, guess what my pinging issue was. The mark on the harmonic balancer I used relates in no way to the scale on the 2.8L timing cover. My timing was waaay the heck advanced. Brilliant. I ended up pulling the distributor and converted to DIS, so no more faffing about with that.

Also, I finally put a gauge on my fuel line. 10.5 PSI. I think the injectors are spec'd for flow at 13 PSI. So my 46# injectors are only REALLY flowing 41#.

I'm sure it didn't help things either that comp cams order was mispackaged. One of my twelve 1.6 ratio rockers was actually a 1.52. The ratio was stamped on the rocker, but I didn't notice when I installed them. The mismatched rocker ended up on the intake of cyl# 1. Also, I had a bum lifter that wouldn't hold oil, so my engine would tick every cold start until it pumped back up (intake, cyl# 2). I recently got around to fixing those issues, so my cylinders should be more-or-less balanced now.

I both ordered an adjustable fuel pressure regulator and some larger injectors. My BLMs running off the stock BIN indicated a lean condition across the board. Between the injectors and the regulator, I think I can rough in the flow to make the stock tune more workable. Hopefully finally wake up the top end of the engine whilst running TBI. I do have my multiport components mocked up on the stand, hopefully those will come back someday too.