Hey guys, I have a intercooler Procharged 89 with a zf6, it was originally intended to be a California legal build but I found a work around so emissions are no longer a concern for me.

I found a ridiculous deal on a Miniram intake (has the TPIS fuel lines and rails)with a Holley throttle body so I picked it up.

in terms of tuning what needs to be adjusted in the prom, I’ll be using tunercat.

I will also be deleting egr as well if that makes any difference and I’m avoiding a Holley terminator or aftermarket engine management at the current moment since I really like how the car runs right now. I would like to use the factory ECU with the FMU and MSD BTM just for the near future as I’m trying to avoid dumping large amounts of money into the tuning at the moment.

 

As someone who has owned a Miniram since 1999, the main thing about the Miniram is getting the accelerator enrichment (AE) correct. The miniram is notorious for off idle stumbles due to tip-in fueling issues. It can be a frustrating manifold to deal with at times, as I struggled with it for years, but over that time, I really learned how it works.

Over the last few years, I had discovered that using all of the AE values from the 92-93 speed density LT1 Corvette worked absolutely beautifully. However, I'm running a 90-91 speed density TPI system, and it just so happens that GM used the exact same AE fueling algorithms in the code between those two systems.

The other thing is the relatively poor air/fuel (A/F) distribution at lower engine speeds. Both from side to side (which often results in the dreaded "split BLM" issue, which you can search on and read about), as well as from front to rear.

The Miniram unfortunately is not well designed to run on a batch fire system, so when GM switched to sequential EFI in 94, you can see in those calibratoins how they trimmed the fueling from one cylinder to another. I ended up brute forcing some mechanisms to help approximate this.

May years ago, I generated a small idle air manifold to distribute air equally to the cylinders. Rather than the cylinders pulling air from the main plenum, the throttle blades are pretty much fully closed at idle, such that they pull air through this idle air manifold, which got rid of my split BLM issue.

https://www.thirdgen.org/forums/diy-...ram-split.html

Then more recently, it dawned on my how I can roughly approximate GM's fuel trimming from front to rear on the sequential EFI systems.

https://www.thirdgen.org/forums/diy-...injectors.html

But putting all of the above together, I've finally conquered this thing. It always had run well, but my perfectionist side always felt like I was leaving some performance and driveability on the table. Most people wouldn't go through all of the trouble I went through with this thing, but I really liked the manifold and was determined to tame it.

I see you're running an 89, so it'll be a little different in terms of the tuning. If you had 90-91 system, I'd offer to send over my Miniram start bin, but it won't work on a 89 system unfortunately.

 

Thank you for this, it gives me an idea on where to start on my 89. I'll have to start playing with the AE tables after I get this installed.

 

If you look at post #11 in that thread about the 10% bigger injectors, I give some thoughts on how to approach a 87-89 $6E bin based on my experiences with $8D.

 

IDK...this thread (and specifically the argument posed in the 3rd gen link) seem valid enough that all front-loaded EFI intakes should sit up and take notice. This is a very interesting subject...at least to me.

THANKS FOR YOUR LINK ABOVE!!!!!!!!!!!!!!!

 

Thank you for your efforts and hard work, Thank God for you being a perfectionist. Can a mini ram be tuned via different size injectors to solve the fuel doodling and the tip in stumble? I prefer the 85 to 89 MASS Air Flow and the batch fire... The fact that the mass air adjust to the real time atmosphere density and temperature has worked well for me at sea level. I notice on a cold night that the car picks up a noticeable amount of horsepower... I was thinking a mix of 24lbs and 30lbs injectors? What say you... Cheers, Jarrod

 

I don't think you can fully solve the tip-in stumble without careful tuning of the AE fueling. It might improve things a bit... some of the tip in stumble could be due to the fuel distribution issues.

Besides, 24 and 30 lb is too large a spread. If you're going try to do what I did, you should try to keep the spread to about 10%...

So if you run 24 lb right now, you could put 25-26 lb on cyl's 1-4, and leave the 24's on 5-8.

Let's say you run 26 in the back and 24 up front. Then you'd want to change your injector constant to 25 lb. I run 32 up front and 30 in the rear, and set my constant to 31.

 

Just an idea as this investment has a lot of other benefits: You may want to consider a Holley EFI system so that with a Dual Sync or added cam position sensor, you can trim the injectors individually at low load and RPM as well as high load and RPM, and huge latitude with adjusting acceleration enrichment, as well as data logging tools to see what AE is doing and the resulting wideband reading, engine RPM reaction, etc. also if you’re not getting as much air and fuel in a certain cylinder or 4 at idle, those cylinders need more timing at idle, you can do that also.

 

Agreed... if you can run SEFI, I would.

I was too lazy to switch over so I brute forced an approximation of the benefits of SEFI. For me though, I'm completely satisfied with how it runs.

 

Fantastic for us batch fire fans... be an outlier... the force is strong with this one... lol, Cheers... Does anyone know if DFI still sells Accel stand alone computer or is it ancient history... everyone tell me the Holley is the way to go today.

 

I think those are long since gone.

But this guy has one for sale

https://www.thirdgen.org/forums/engi...l-dfi-7-a.html

 

I run a 1988 computer with mini ram intake on a 355 and it works fine, tune in the acceleration enrichment to eliminate the tip in stumble and the car drives fine. So the short answer is yes you can make it work.

 

The blower will likely exacerbate the mini ram's issues.

Here's data from a blown mini ram car and raw dyno data included: https://datazap.me/u/tequilaboy/test...3&mark=139-214

Looks like it backfired on the dyno. Hot boost, not sure if they were using water/methanol injection during this pull or not. Hard to know what somebody else is really doing. AFR looks good to me.

This was a collaboration between myself, Blowerworks and Simpson Racing in BC Canada. Even with my support, a pro tuner had issues tuning it on his dyno. I think they blew it up in less than a year.

Note: This car had about 6 months of road and dyno tuning (December 2018-May 2019) with the mini ram intake prior to the log that I posted above. Do not underestimate the tuning effort involved. I supplied at least 30 bin files. Chris was also making changes locally with an ostrich, so probably 100+ iterations.

87 Corvette
Stock displacement
AFR 195 heads
Comp 12-502-8 camshaft
ProCharger D1 (non-intercooled)
Snow Performance water-methanol injection kit
Holley 48 lb injectors
Aeromotive 340 Stealth in-tank pump
Edelbrock TPI lower and runners (9/2018) -> mini ram (12/2018).
Headers
Stock TB
3.73 rear gears
A1 torque converter

 

Not trying to be argumentative... just discussing here...

Mine worked "fine" too, before I fully deciphered this manifold and effectively re-engineered it to run on batch fire (as described above). Along with the tuning discoveries I made about using the early speed density LT1 accelerator enrichment fueling.

It literally runs like a different car now.

 

No offense taken.

I have run many mini rams and some lt1's on the factory batch fire and they seems to run fine to me. That does not mean your modifications do not make them run better. I am just listing my experience of a fine running car with the factory computer.

I have never tried your modifications and only if I did could I really comment on them.

The 1992 and 1993 cars from GM ran on the factory batch fire system, in 1994 they did switch to sequential fueling with modified cylinder fueling until they hit around 3000 RPM and then it reverted back to same fueling per cylinder, so there may be some benifits to trying to improve low RPM light throttle air distribution, or fuel distribution.

 

Everyone seems to focus on fueling being so important, but that can vary quite a bit and the engine still runs fine. You may lose a little power or EGT’s may be a little high right at stoich, but without extended data / testing it’s hard to tell. With forced induction, that wide range narrows a little bit under power.

Ignition timing, however, makes a big difference, and can also cause more damage. They are inter related as more fuel charge, more air charge, and more fuel and air charge combined, will accelerate the ignition event quite a bit. Meaning the ideal ignition timing is much lower for the same cylinder pressure spike timing… conversely if some cylinders are getting a lot less air and/or fuel charge, ignition timing should be advanced to prevent combustion process continuing during exhaust valve open event. Can’t do this without individual coils and cam position sensor, and sequential ignition system programming. And even then, it’s an approximation based on methods to determine the manifold pressure or resulting combustion variation per cylinder, not easy or quick to do, so we would make some safe guesses to help out. It’s not a complete guess and it shouldn’t be, but based on data such as flow data on the manifold or even OEM fuel calibration engineering data… to be used for ignition also, for example if you’re cutting fuel by 15% on #8 cylinder, you can find ignition data for the same RPM and 15% lower manifold pressure on the timing table, assuming you have a well developed timing table… and this will help. Also you can’t assume that #1 and #2 are getting most airflow as sometimes they get less… and for example the monoblade helps get more air to #1 and perhaps even #2 if it was previously restricted.

 

Agreed on the ignition timing. The Miniram likes a lot of spark timing in the low map regions and at idle and in the low map regions of the table.

 

Found a dyno sheet to go along with the log data and dyno data that I posted above. It didn't really make much power and the torque curve is a bit strange, but at least its rising. Another 1,000 rpm would've been interesting to see.