I ask because my brother's 87 GTA with Minirammed 409 decided to eat a couple of it's cam lobes for absolutely no good reason recently. Got about 2 weeks of good running (fantastic running, actually) out of it after discovering the injectors were not what they were supposed to be and now this! Oh well, stuff happens. Gives him a chance to put in a bigger cam that the engine really wants......... which brings me to my point:

Cam coming out is a little Crane 266 Energizer single pattern cam with 210* of duration @ .050 and a 110 LSA.

Cam going in will be a Comp Cams 270 Magnum single pattern cam with 224* of duration at .050, still on a 110* LSA.

This is a Mass Airflow type FI system, not speed density. Will the custom chip that was burned for the little cam work OK with the slightly hotter cam? I've found MAF-type systems to be very forgiving of cam changes in the past, unlike speed-density types, but we're talking an additional 14* of duration (a lot) so I figured I'd ask for opinions/expereince.

 

Not if you are maxxing the MAF. Then you get no fuel correction.

The only "way around it" is to tune similar to SD where you add fuel via the Power Enrichment Table to compensate for the lack of fuel due to NO MAF reading beyond 255 gm/sec.

So, yes you need a new eprom.

 

Should have mentioned that it is not the stock MAF. It is a TPIS high flow unit and it is not near being maxed out with the smaller cam (190 g/sec peak reading). With the bigger cam we might be getting getting near the top of it's range, but I doubt it.

The current custom chip is a TPIS chip since they are the only ones who really know the flow characteristics of their high flow MAF.

 

Believe as you wish.

 

Um........................ HUH?

I wans't trying to be a smart-***. I just mean that Diacom says I'm not going beyond about 190 G/sec on the high-flow MAF currently. That's as high as it ever reads. Obviously, it's taking in more air than that, but it does not max out the MAF flow value. The reaosn we have a TPIS chip is because, like I said, only THEY know what the actual flow characteristics are, so only they know how much fuel equals a MAF-"INDICATED" 190 g/sec.

What did I say to **** you off?

 

Nuff said. Do a search on the DIY Prom Board on "TPIS" and see what you get. BTW, for a company that "knows it stuff", do you realize that their "relocated MAT" does ABSOLUTELY NOTHING GOOD for a TPI MAF car?

FYI, the cam you are going to is a radical change from what you are currently using. There is apt to be "other issues", like working on the IDLE which your current chip can't deal with. MAF systems suffer from "reversion" with cams that get "lumpy".

If you want MAX PERFORMANCE, go to the DIY Prom Board and learn to burn your own. There is NO WAY someone can burn an "optimal" eprom by "specs". I can burn a pretty good one just by specs, but when you have "hands on" access to it, it's like night and day. However, the cost to pay someone to do that is prohibitive. Therefore, you got to do-it-yourself.

I guarantee that once you start getting into "tuning" it yourself, you'll join the ranks of saying "I can't believe that TPIS had the nerve to charge me $500 for the piece of crap they called an eprom".

PS: I won't even get into the issue of "high flow" MAFs. I'll let you read up on that yourself. Be prepared to take a Valium or two when you find out what you've really done.

 

OK, I'll check it out.

I know it won't be "optimal" sticking with the chip we've got now. I just want it to run acceptably and not hurt the motor from running too lean or too much advance, etc. FOR NOW. Burning our own chips is coming soon, just not right now. We're focused on just getting the new cam physically stabbed in the motor for this weekend.

I guess we've been lucky with this chip from TPIS so far. It has run the motor well with the small cam it's got in it currently. Of course, all that will likely go out the window with the cam change, but I haven't had the kind of disaster that others have reported with TPIS chips.

 

Are you BLM/INTs ALWAYS 128/128? If so, then your lucky. If not, then it's off.

 

No, the BLMs are in the 122-125 range. Not perfect, but good enough for government work.

My all-stock 94 Formula has BLMs that vary from 118 to 123 (stock 43 PSI on the regulator). So I guess it's better than some stock programming at any rate.

If I was getting constant 128/128s out of it I would know that something was wrong. I've never seen any car with any programming nail anything like consistent 128s. It always varys some small amount in my experience- even from day to day under changing weather conditions.

 

WOW ,
That is reall y close for a TPIS prom...
You can probably get away with it and fuel preassure but you will be greatly rewarded to spend $250 as opposed to $600 to buy your own burning equipment and jump over to diy prom board and let us teach you of all the benifits (drivability) is a huge one not to mention the power gains.

 

Btw, 255/grams converts out to 522CFM at sea level, normal atmospheric pressure.

While I agree with Glenn you should mod your prom a bit, I don't think that cam is big enough to cause a problem with the MAF
setup.

I also agree that the TPIS chip may do more harm than good.

HOWEVER, I am running a stock chip from an 87 firechicken, on a 89. My cam is 224/230 502/510, and so on, supercharger, etc. I'm not having any major problems. I was running a little lean in the front cyls, but I think running a too hot plug was the major offender. I went a little colder, and i'll prolly back my timing off a bit. I'm running 15 degrees base timing, and the ECM advances about 24 or so. I'm thinking of jumping down to 8 degrees initial timing.

The problems with the 165 (maf) setup I have are:

1> Under boost, the ECM has no idea whats going on, but no
detonation. (also no idea what the a/f ratio is..?? power loss?)

2> Sometimes when I come to a stop, my idle floats at 2k, for
about 20 seconds, then comes back down to 400rpm..
This maybe cuz the chip was for an auto, I'm running T5??

3>I don't like my timing curve.

4> I'd rather change injector pulse, than increase rail pressure.
The FMU for the vortech basicly shuts off the return line,
maxing out the fuel pressure at the rail. Is this a good
approach?

I'm considering going SD, but I havn't educated myself enough to know if its gonna really help, or if assigning 2 registers to the MAF
count in the 165 code, rather than 1 8 bit register would be a better approach. Not seeing the code, I dunno..

-- Joe

 

Well you can get rid of all your driving foes by tuning your own proms,you can get better milage by tuning your own proms,
you can totally dictate your timing curve by tuning your own prom
(you can throw away your timing light)you will never move dist.
again.
If you switch to SD you will not have no choice but to tune your own proms.. unless you try dial-a-chip.
And then you will see how much better off you are by tuning your own proms.
Much easier than you think,and many of us are here to help.

 

I wanna educate myself better on the timing capabilities of the ECM.

Could you set base timing to something like 2 degrees for easier/quicker starting, but have full control over advance?
I know the stock ECM advances like 24 degrees or so, but didn't know how much control over spark curve you have.

-- Joe

 

You sure can,
Here is a pic of a timing table ,top line represents load or map
kpa and side is RPM - you are seeing amount to be advanced over base timing.
As you can see you can change advance at any rate you want
you can change any of those advance numbers in that table.
There is evan a table extention for higher rpm.
opps sorry piant brush (print screen is to big a file) ill copy and paste half of it
Map KPA
20 30 40 50 60 70

degrees advance
20.0 20.0 20.0 20.0 20.0 20.0
20.0 20.0 20.0 20.0 20.0 20.0
20.0 20.0 23.9 23.9 23.9 23.9
20.0 22.9 26.0 26.0 26.0 23.9
20.0 25.0 28.1 28.1 28.1 26.0
20.0 25.0 32.0 32.0 32.0 28.8
25.0 34.1 36.2 33.0 32.0 28.8
29.9 34.1 36.9 34.1 34.1 32.0
29.9 34.1 38.0 35.9 35.9 33.0
29.9 34.1 38.0 35.9 35.9 34.8
29.9 34.1 38.0 35.9 35.9 32.0
29.9 34.1 38.0 34.8 34.8 29.9
29.9 34.1 38.0 34.1 34.1 27.1
29.9 34.1 38.0 38.0 34.1 28.1
29.9 35.2 40.1 40.1 34.1 28.1
38.0 40.1 40.1 40.1 40.1 33.0
38.0 40.1 40.1 40.1 40.1 35.9