I have an 89 six speed Vette with a 396 small block. I'm in the process of tuning the car now. My question is I know that removing screens, removing fins and even using an open air filter lid can cause the MAF to under report airflow, but what about what is behind the MAF? I have a 396 cid motor with a miniram, headers, AFR heads, etc. If everything is stock from the MAF forward, shouldn't the airflow be reported correctly (up until its limit) if the stock MAF tables and scalers are used? Or am I missing something here? I am having problems dialing in the tables correctly with my ported MAF. I respectfully ask to please hold the "Switch to MAP" comments.

Thanks,
Jason

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89 Vette 6 speed
CNC heads, crane cam, Miniram, headers
Soon to be 396 Small Block!

 

89vette, you are going to have to do a lot of tuning. First off, what size injectors are you running? You are going to need a chip burnt so I would start to get the things that you need to do that; like prom burner, prom eraser, a couple of proms, a scanner(or a laptop, a cable, and some software). It takes a while to get used to burning chips but once you get the hang of it, it just takes time and patience.
You could also get some aftermarket company to do it for you, but if you do, dont do it over the phone. Let them have your car for a few days and do it right(on a chassis dyno). Otherwise they are just guessing. Goodluck!

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355 10:1 , AFR 190 heads, LT4 HOT cam w/ 1.6 roller rockers, complete Superram intake, 58mm BBK TB, 24# injectors, screens out of MAF, MAT relocated, March underdrive pulleys, Streetdampner, Crane HI-6 ignition, 160 thermostat, K&Ns, TES headers(Jet hot coated), Mufflex 4' cat back, B&M shift Kit, 2500 converter, and 3.27s. Chip is custom(doing it myself) Just got a 2 1/2 Harwood and soon to be painted.

 

Using an SLP cold-air box with associated ductwork and definned gutted MAF, combined with a 'stock' 305 (peanut cam) and SVO 24# injectors at 45# FP, I had to specify 20.5# to get my BLMs to line-up at 128. Since the SVO 24#'s should pass 27#@45psig, the 20.5 represents approximately 25% under-reporting, which when you take a visual of the MAF CSA in the outer compared to the CSA of the fins, is probably quite reasonable.

So, if you cut the fins out, expect to crank down your FI sizing by 25%, all things created equal. As for the downstream factors I cannot speak, but I know there are significant issues when you start getting into enlarged cams and funky duration overlap and resonant wave backlash and such.

 

I already burn my own chips. I have Diacom and GMEpro and all burning/erasing hardware. It's been a real challange getting the Miniram tuned correctly. I am running 30 pound ford injectors at about 44 psi (WOT). I have played with injector constants from 26 to 33 and it seems to be happier at 32/33. At 26 my block learns were all 108. I have been struggling with a hesitation and backfire through the intake ever since I put the miniram on. I see a huge dip in O2 volts everytime the throttle is slightly depressed. Last night I put on a stock MAF, stock airfilter and lid. I have also found out that the AE fuel table that affected the hesitation problem the most is AE fuel vs BPW inj. I have set the 8 pulses of AE fuel at:
2.5
2.25
2
1.75
1.5
1
.75
.5

This has helped the most and I may even increase it a little more. Anyway, after putting on the stock MAF and replacing the modified MAF tables with the stock tables and scalers, the car seems to run much, much better. Wouldn't you know my Diacom crapped out on me last night so I have no recordings but SOTP is better. If the gutted MAF is the culprit I will have alot of work getting to perform correct. Also if it works then my thought that what is behind the MAF does not matter as long as the MAF forward is stock. My car seems to be extra sensitive to any changes. My goal is to get all part throttle issues straightened out first then work on PE vs RPM.

Thanks,
Jason

[This message has been edited by 89vette (edited April 12, 2001).]

 

Jason,

A significant number of MiniRam owners (especially the MAF guys) experience the part throttle backfire through the intake. Speed Density guys experience it to a lesser extent but still often experience it. I had this problem and I am Speed Density. I also worked with a SuperRammed vette (w/ heads/cam) that also had this problem (speed density too). In both cases I was able to solve the problem by increasing the pump shot (acceleration enrichment vs. TPS%). Basically, the car pulls lower vacuum at idle which requires less fuel. However, as soon as you 'get on it' the vacuum increases and you need significantly MORE fuel. This, in my experience, indicates that the car likes more acceleration enrichment (makes A LOT of sense when you start thinking about vacuum vs. RPMs vs. the type of changes you have made to the fueling). Anyhow - since I am not a MAF expert I am not sure how to increase acceleration enrichment with the $6E. I DO KNOW that a MAF guy brought up this VERY subject about 2-3 months ago. Search the archives of this board and you will find it.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Trax,

I think that guy was me. There are four tables that affect AE fuel in the $6E code. AE vs coolant temp, AE vs delta LV8 and AE vs BPW inj. and AE fuel decay rate. The AE vs BPW inj. seemed to be the one that has helped the most. The backfire seems to be gone but there is still is a slight hesitation at very low speeds like creeping through a parking lot. I'm a heck of alot closer than I was 6 months ago I can tell you that. The other problem I had was that during cruise I was long term rich and short term lean when say acellerating from 50 to 60 in fourth gear. I think this is where my ported MAF affected me. However I can't verify this yet because my Diacom crapped out for some reason.

 

89 vette, what are you using to edit your bin? I have tunercat (6E) and I dont have any AE tables! That would be very useful....

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355 10:1 , AFR 190 heads, LT4 HOT cam w/ 1.6 roller rockers, complete Superram intake, 58mm BBK TB, 24# injectors, screens out of MAF, MAT relocated, March underdrive pulleys, Streetdampner, Crane HI-6 ignition, 160 thermostat, K&Ns, TES headers(Jet hot coated), Mufflex 4' cat back, B&M shift Kit, 2500 converter, and 3.27s. Chip is custom(doing it myself) Just got a 2 1/2 Harwood and soon to be painted.

 

GMEPro. Contact Terry Kelly at terryk@foothill.net Fantastic software that runs under DOS for the old laptops. Even has a hex editor.

 

Remember, a MAF reports air flow, in any direction. So an engine that has more reversion really can mess things up. Then to add insult to injury removong the fins screens, can aplify those errors. At this stage your just pasting things together. All you need to do is figure out a MAF that will work with set up, just wire in a LS1 MAF and something to translate the info and then you can approch what you don't want to hear.

 

All you need to do is figure out a MAF that will work with set up, just wire in a LS1 MAF and something to translate the info and then you can approch what you don't want to hear.

Grumpy what do you mean by this? I have the car running good except for a hesitation under hi load conditions (like goosing the gas in 5th while going slow). It now very seldom backfires through the intake. Is the 730 easier to tune as far as a pump shot? I would convert but I want to retain my MPG average and range functions.



Jason

 

MPG average, my L98 gets close to US 30 MPGs with Highway Mode invoked.

 

Jason,

Check out the latest Car Craft. There is an article about using a FORD MAF in place of the stock TPI. I have not read the article yet but I believ it is Granitelli that make a conversion adapter for it



------------------
-=Jeff=-
89 Corvette Coupe White with Black Grand Sport Stripe
-=ICON Motorsports=-
Check out my mods on My '89 Vette

 

89 Vette, can you tell me the address of the AE vs TPS%. I dont know how your software looks or if you can even see this but it would be very helpful. This way I can modify my Tunercat tdf file and not have to buy/learn the GMEPro software. Or if you know somewhere that I can get a 6E hack, that would be cool too!
Thank you

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355 10:1 , AFR 190 heads, LT4 HOT cam w/ 1.6 roller rockers, complete Superram intake, 58mm BBK TB, 24# injectors, screens out of MAF, MAT relocated, March underdrive pulleys, Streetdampner, Crane HI-6 ignition, 160 thermostat, K&Ns, TES headers(Jet hot coated), Mufflex 4' cat back, B&M shift Kit, 2500 converter, and 3.27s. Chip is custom(doing it myself) Just got a 2 1/2 Harwood and soon to be painted.

 

There is no AE vs TPS. There is AE vs delta LV8, AE vs coolant, AE vs BPW inj, and AE decay rate.
I do not know where the address are.
Jason

 

Thanks for checking Jason, I appreciate it. Which table do you feel helped the most with the initial lean condition when you hit the gas?

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355 10:1 , AFR 190 heads, LT4 HOT cam w/ 1.6 roller rockers, complete Superram intake, 58mm BBK TB, 24# injectors, screens out of MAF, MAT relocated, March underdrive pulleys, Streetdampner, Crane HI-6 ignition, 160 thermostat, K&Ns, TES headers(Jet hot coated), Mufflex 4' cat back, B&M shift Kit, 2500 converter, and 3.27s. Chip is custom(doing it myself) Just got a 2 1/2 Harwood and soon to be painted.

 

The AE fuel vs BPWinj. From what I gather, it modifies the 8 AE pulses. Stock is set to .5. Maximum is 3.99. I set them to:

2.5
2.25
2
1.75
1.5
1
.75
.5

I still need further tweaking though. The other table that helps is the AE vs LV8. You have to be careful because you can load up the motor with too much fuel when its spread out too far. Then you have to start increasing the decay rate and then it seems you end up where you started. I just don't fully understand what each AE table does. I know enough to be dangerous!

 

Glenn,

Care to detail how you're getting 30 MPG? I'd LOVE to be able to enable highway mode in my GTA as well. Pointers?

Thanks!

--andrew "MAF now but going MAP soon!" g.

 

There will be a future article on Highway Mode when time permits.

 

I would play with the a/e vs delta table more. I think it would be closest to a/e vs tps. That is the table I had to really play with in my speed pro to get the backfire to go away.

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87z 383,afr 190's, comp hyd roller(242/248-.540/.562,114 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, tremec 5spd, , 1,3/4" slp headers, speed pro bank to bank-wb02.
"Just remember children, no man can beat you once youv'e found the cliterous." 'chef'

 

Even with my WB02 ,and cruise af table set to 15.0-1 I get sh!tty gas mileage.

 

You should try 16.0-1 or even higher. I have mine set at 16.5 and the O2 sensor is just into the single digits, but does respond to throttle inputs, and I'm not getting any spark knock. The stock settings were around 15.3 at lower LV8s, so 15.0 isn't doing much as it's just above the stoichiometric 14.7 ratio. I know Glenn and Bruce have had success running at 17.0 or a little higher, but you really have to be monitoring things closely/carefully at that extreme.

------------------
Greg Westphal
'87 IROC 305TPI/A4

 

Also, you REALLY need to have GOOD BLM/INT values. Poor BLM/INT values can either cause your car to be too lean/too rich or it may not even work. On SD cars, it is dependent on the Purge Canister working and if the BLM is below 115 (I forget what # it has to be above), then the Purge Canister won't work, and thus not let Highway Mode work.

Also, it should also be done in conjunction with the Highway Mode Spark Advance to get the best gas mileage while retaining decent throttle response. Too low of HMSA results in a "spongy" throttle feel and you don't get as good as gas mileage as you could.