What is the range of the 2 and 3-bar MAP's? Can the 3-bar MAP be used with the 749 for very high boost applications?

 

The code needs changed to use a 3 bar MAP. There are 3 bar bins available. Try www.syty.net and search for 3 bar bins. cheers, BW

 

The 2 bar MAP allows for up to 15 PSI of boost.
The 3 bar MAP is good for 30 PSI.
The 3 bar patch isn't a perfect, but more then close enough.

 

I think I'll stick with my 165 and Superfueler. I can adjust the SF as high as I need. I'll be pushing 20+ psig..

Willie

 

And what for timing control?.
The higher you raise the pressure demand on the fuel pump the less fuel it delivers. The fuel pump can only do so much work.

I run, 24-26 PSI of boost and a 85% Injector Duty Cycle using 60 PPH injectors. Actually that an average PPH figure, since I use 6 of one size and a 7th of another.
And have been running this much boost for about 3 years. At 28 PSI I lifted a heat and popped a headgasket, no detonation, just fatigued the gasket. And dropping to 26 haven't had ANY problems.
Also, have done this with MAF, and MAP systems and have some time in each, but if you want to reinvent the wheel, have a good time, just trying to save you some effort.

 

And what for timing control?.

I've been using MSD's 8977 Multi-Function Programmable Timing Controller. I can map timing retard via points on a graph -- totally user friendly.

I should have added previously that I use 23# injectors (rear two cylinders use 24#ers) and have not seen over 90 percent duty cycle. My Superfueler uses three 75# low-impedence injectors.


The higher you raise the pressure demand on the fuel pump the less fuel it delivers. The fuel pump can only do so much work.

Understood. I never see over 65-psig. I also run a Kenne Belle Boost-a-Pump set to about 25 percent increase in voltage.


.... popped a headgasket, no detonation, just fatigued the gasket.

What kind of gaskets do you use? I'll be using Cometics when I reinstall my engine in the weeks to come.


....but if you want to reinvent the wheel, have a good time, just trying to save you some effort.

It will be more time and effort (and $$$) to convert at this point, much less tuning. Since I've been using the 165, Superfueler and MSD 8977, I see no advantage to converting at this time. I appreciate your comments though.

My EPROM has already been tweaked to work with my prior setup (14-psig). Because of my plans to significantly increase boost in the months ahead, all the "tweaking" is on the Superfueler and timing retard. Currently, I need a maximum of 12 percent duty cycle on the three SF 75#ers, so I've got a lot of room for growth. Now, if I were starting from scratch, I'd definitely go the 749 & 3-bar MAP avenue, but......

Willie

 

If your distribution is close your close to having the fuel convered. Didn't realize the SF used that large of injectors.

It is in large part having it tuned well that makes anything work, and if what you have is tunable and works for you that's the most important thing.

Just a FWIW, in playing with my MAF setup, I added some stuff so that it was boost referenced for timing and spark and it made a big difference in drivibility. As you've probably noticed as you go into boost, and then again as you cross about 10 PSI performance really wakes up, and for me it's been getting those transistions right that's mandated going MAP.

It was a set of Felpros. But, I'm not holding them to blame. I used the 28 PSI of boost, alot, and for a while had marginally enough injector.

Seems like the Buicks have had good luck with the Cometics. My new motor is going to be using them, too.

 

Didn't realize the SF used that large of injectors.

Greg Carroll says you can use any size injectors you want, low or high impedence.... Nice system.


Just a FWIW, in playing with my MAF setup, I added some stuff so that it was boost referenced for timing and spark and it made a big difference in drivibility.

What "stuff"? You've got me curious now.....


It was a set of Felpros. But, I'm not holding them to blame. I used the 28 PSI of boost, alot, and for a while had marginally enough injector.

I'm amazed they could withstand even 20-psig...


Seems like the Buicks have had good luck with the Cometics.

Exactly. That's why I'm going with them.

BTW, I'm making a "few" changes to strengthen my 305. Here's but one:

Willie

 

Sorry to butt in, but Willie do you have part numbers for the studs/bolts you used . thanks, BW

 

Originally, I bought the Milodon conversion caps (gold in color) and took them to the machine shop. When I returned there one week later, I saw the ones in the pic installed!! Comparing the two, it was obvious the installed ones are much beefier. I didn't get the name, but I'll be stopping at the shop tomorrow (08-04-03) and will find out -- need to know for my records too!!

I will tell you what I do know. The inner "bolts" are ARP studs. I'm thinking the outer bolts are 12-point ARP's, but need to confirm.

Willie

 

thats a standard milodon,moroso,gm performance splayed cap conversion kit. will work with all 68 and up sbc chevy engine execpt for the 400.

 

Thanks Willie. I bought a set of caps too, without bolts/studs. I figure the inners are just standard 2 bolt studs, but I don't know what outer bolts to use. BW

 

sorry bob i didnt know that you didnt have bolts. um try 5/8 14 tpi. ARP can definately help you on that. tell them what you got and what ou need. buying the bolts individually is cheaper then buying a kit if you know the sizes you need.

 

You said the 3 bar patch isnt perfect but its close. I've only heard bad things about it ... but never specifically whats bad except that the code is hacked/patched. I'm wondering if you have any more details about what is questionable about the 3 bar patch? I'm still getting ready to do a 730 -> 749 swap in my 91Z and I want to tune with Tunercat R_T. Since I had doubts about the 3 bar code, I've been planning to stick with the stock 2 bar sensor. I would prefer to do it from the start with the 3 bar sensor so I dont have to swap them for my future motor, but I dont know enough about it to feel like it will be reliable. What do you think? Is the 3 bar patch streetable? Thanks!!!

 

Ditto..

Cheers,

 

The only drawback I am aware of is the loss of resolution..

Example.. Main Spark Advance Table across

2 bar version

17 columns going to 190 Kpa.

3 bar version

17 columns going to 285 Kpa.

 

FWIW, Ken C was able to increase the size of the VE tables (at least in TBI & where there was room on the prom) to get resolution back into them. Part of the explanation was posted here: http://forums.corvetteforum.com/zerothread?id=547494

His eMail address is on that site. Haven't tried to do it yet myself, so I don't know if it applies here, but I thought I'd pass along the idea.. HTH.

 

The only bad thing with the patch is that it's not as linear as say GM would have done it.
PERIOD.

As far a resolution goes, look at the state of the art Accel Gen VII VE tables with a 3 bar. It's like 18-22 K/Pa per step, as I recall.

The 3 bar patch is just fun.
BTW, I've been running it for several months now, on my own car.

 

fun should have been fine, but either works, LOL

 

As I see! Makes a little more sense now. Well if you trust it enough to run it on your car Grumpy, then it must be stable. Definately something I'm going to consider and research while I get ready to do the swap. Thanks for the info Guys!!!

BTW, what Sy/Ty websites do you guys post on to talk about the 749 ECM/PROM? I've tried a few but nobody really seemed interested. Maybe if I know some sites with good info I can go Search till I pass out! Thanks!!

 

I normally graze thru www.syty.net every couple of weeks to see if there's been anything new.

They're pretty well established with the Ultrachip as being the answer, and for 90% of the trucks it is.

About the only odd thing with the Sy code is that the ALDL BPW flickers. But, it's nothing to worry about. Hmm, maybe that's what folks are complaining about.

 

You guys got me to thinking about swapping to the 749 again... The first step would be to locate a wiring harness. I know a 730 from a TPI harness will work, but aren't these almost impossible to find? What others would work? Not the L03, right? How about a MPFI V6 harness?

Willie

 

you have mail.

 

Just reuse your 165 harness..

not hard to repin and change out a few wires.

See Mike Davis's site, he has a165 to 730 repin chart.. then changing to a 749 is just 6 or so differences.

See Bort62's site also.

BW