I found someone who is going to help with my harness and he recommended going to Speed density from my current MAF system. I think he is right :-) The engine has AFR heads, Hooker LTs, Crane Cam 502''/510, 10.5 compression, all the good stuff. Besides him modifying the harness I will need a MAP sensor, change my computer to a 90-92 model(I have a new computer, so just exchange) and get into prom burning(Will be very soon) Is that it. Is the connector to the MAF just changed to work with a MAP sensor. Oh yea all those MAF burn offs and relays, huh? Sounds like a pain to me. All reccomendations appreciated.

Thanks

Chris :lala:

 

I am glad to see that you will be going into eprom burning, this will make it a lot easier for you to try things. Also, I recommend that you get your eprom burning stuff BEFORE you convert to SD. This way you can "test" on your MAF setup first - costs nothing to work with the MAF.

I say this because I have worked on both, and I will agree that I PERSONALLY prefer SD. But I have been able to make MAF cars run on some setups that you would have never thought possible.

One friend has a 1989 MAF 383 with Miniram, AFR 195 Comp Ported w/2.05 intakes, 222/230 @ .050 .53x/.54x (w/ 1.6 RRs). When he got his engine completed, we were planning to swap to SD but decided to see how far we could push the MAF since it is a lot easier to burn an eprom than swap ECM/harnesses.

I was predicting that he'd max the MAF at around 5,000 rpm, which came true. We had to play a little with the idle but very little and the engine idles remarkablty smooth - almost too smooth if you like a bit of "lope". Some minor "tweaks" to the MAF Scalar Tables (not for the faint of heart and not really necessary) and we had the car running great - up to 5,000 rpm. Unfortunately, his setup makes max power @ 6,200 rpm.

So I suggested using the "PE %Change AF Ratio vs RPM" to add more fuel after 5,000 rpm to compensate for the lack of fuel correction by the MAF beyond this point. Worked like a hot damn.

While we would still like to install a WB O2 sensor on it to fine tune the mixture @ WOT > 5,000 rpm, the car is currently peforming beyond our wildest expectations. So much so, that he has completely abandoned the idea of going SD and I agree with his decision - he has no need to go SD at this time. Maybe if his MAF dies he'll look at it or if he decides to go "Ram Air" and get the "clean shot" into the intake. But we have made his car run just fine on the MAF setup.

Through the "PE %Change AF Ratio vs RPM" table, the MAF system can have fuel correction up to 6,400 rpm. Yes, you must "manually" set it, but you have to do this with SD also. For WOT, at those rpm levels, both SD and MAF really need a WB O2 Sensor so neither has a real advantage there.

The difference comes to "fine tuning" for "part to moderately heavy" throttle. With MAF, if those MAF Scalar Tables need to be tweaked, you can really find yourself in a "Chinese finger puzzle". I won't get into the nitty-gritty, but let's just say that it is not easy, especially if you have to raise an "upper boundary" on one of the 6 tables. It requires a complete "rescaling" of ALL the Tables for EVERY ENTRY. At which point, you SHOULD go to SD since it will be easier to tune the VE tables for SD than rescaling the entire MAF Scalar Tables.

Also, we have found that at a particular "flow" for MAF, it can be 128/128 perfect at one particule rpm/load but at different rpm/loads (with the same air flow), the engine may be leaner or richer. We have gotten it pretty close at this time, but there are a few "oddballs" that he has chosen to live with.

SD is more time consuming to initially setup your VE tables, but it isn't as time consuming or difficult as some would have you believe. All I did on my car is drive around with my scan tool in a variety of enviroments over a couple of weekends, noted my BLM/INT values and adjusted accordingly. Did a little more driving - everything was closer but tweaked a bit more. Until I was basically 128/128 throughout all load/rpm ranges of my engine.

What I prefer about SD vs MAF, is that if I have a particular load/rpm value that is slightly off; when I make a change, it affects ONLY that rpm/load range - nothing else. With MAF, it measures air flow - so you may correct a flow reading at a particular load/rpm but that same flow may occur at other rpm/loads and now they are affected (when they may have been perfect before).

So, that in a nutshell is the "tuning differences" between MAF and SD. As I said, MAF can be pushed a lot further than many people originally thought, thanks to the "PE %Change AF Ratio vs RPM" table. I say, give the MAF system a try (but do convert to the 1989 MAF bins, they have better MAF Scalar Tables). It costs nothing more to give the MAF a try first.

You might end up as my buddy and decide that the MAF works just fine. :lala:

 

I had almost the exact same set up as Glenn is talking about above except mine was a 396. I had a tip in stumble and intake backfire that I could not get rid of. SD helped it alot but it was still there. It was not until I swapped to a Super Ram that the problems went away. If I had stayed with the SR I would have had no reason to switch.

 

Well, the motor is already out and I have a new computer that I can trade for an SD computer for free at my local parts store

 

Jason, my other friend had basically the same setup as you originally had except 13 less cubic inches and he had an automatic. Funny thing, we have NEVER noticed the "backfire/pop" with his setup.

I suspect the problem was the combination of Miniram, cam and manual tranny. Manual trannies seem to require a complete "rethink" when used with a Miniram. I would have like to spent more time studying the approach used on the 93 SD LT1 motors with a standard. I think the answer would be within their programming.

 

Glenn,

I don't regret my decesion one bit in switchign to the SR. I picked up 54 ft lbs of torque and the car just rocks. I need more upper RPM HP though as my car makes its 400 FWHP at only 4600 RPM!

Looking into reworkign the AFR heads and having my Super ram ported further. Alot more in fact.

Jason

 

You will also need a Knock detector and speedometer pusler for the SD unit

 

He will need a knock sensor but the speedo can be used as is, just requires a prom change deselect "mag vss sensor".