Hi guys, I finally cleaned up the wiring in my car and got the datalogging back in business, so I can see what my newly Stealth Rammed 327 is doing now. My factory tach reads low at higher rpms (quite low -- 5500 is 6375 rpms as indicated by Tunerpro. Woops!). The car is still pulling harder at my 6300+ shift points. Wow! Thank *** I got rid of the TPI, this thing flys. Anyhow, at 6300 rpms, I was reading 250.35 grams/sec, and at 6375 249.87 grams/sec. Both of these readings were at 91-92 mph in 3rd gear (4 speed muncie). I also read 252.96 grams/sec at 87 mph, 5850 rpms, from another run tonight, 252.78 at 64 mph and 5700 rpms, and 252.93 at 69 mph and 6225 rpms (the 64 and 69 mph data was back to back, so it looks like the MAF is just about totally maxed out and not climbing even as rpms increase). I can't believe a little 327 is maxing out the MAF. This car should be running mid to high 13s in this state of tune right now, its not like I have an 11 second car with a MAF still on it. Other than add a little more PE at 6300 rpms, what else should I be worried about?

 

You don't have too much to worry about. Sounds like you are barely maxing it out and you still have plenty of control left with the PE tables. I'd stick with the MAF and just enjoy One thing though ... you might not actually be hitting the 255 limit until later due to the table that provides for max flow at particular RPMs. You may want to consider jacking up that table and seeing what you REAL airflow is. You might be hitting the maximum amount earlier than you think.

327ci? My little 153ci 4-banger hits over 280g/sec

Tim

 

In Rbob's Maf post it lists the unlimited MAF airflow adddress.
Just put that in your aldl & log.

 

What those guys said and... 327 small, HA. Remember, air flow is very proportional to horsepower. A small motor reving high will make as much horsepower as a large motor at lower revs. Displacement doesn't give you more horsepower, only more horsepower potential... horsepower is in the heads!
Also, maxing out the MAF or even getting to the point of being THAT close would make me switch to SD. That's just me though. Or upgrade to a larger MAF with a translator but I think that's a patch job since the ecm is still only 8-bit more reason to go SD.

 

Thanks guys. This has me a little concerned just because at 6375 rpms, I am still not past my peak hp yet, and I was looking at going with an even larger cam, this time a solid. The Holley Stealth Ram will let me make peak hp around 6800-7000 rpms with the 327 if I wanted to spin it that high, but now it looks like the MAF won't be giving me any resolution up that high. I have the "max air flow table" maxed out at 255 g/s above 4500 rpms, so the table is not filtering the readings. I don't hit any of the table maxes at lower rpms, which makes sense with my smallish engine. I'm just getting really rev happy because getting rid of the tow-truck style low revving TPI has this engine screaming at high rpms like it was back in the carb days.

 

You might try looking at a hac for the 8D, and make your own discision about what to do.

Might even data log a run, and look at the LV8, and when it pegs. The timing table is based on the LV8 calculation, not just the air flow.

To some, close enough, is good enough for timing. IMO, I haven't seen any 3rd gen hac that suffers from too much table resolution.

In doubt?, try looking at a OBDII, say an 01 T/A, and look at the table sizes. They're huge compared to the Gen III stuff.

 

i got a translator i need beta tested. hit me up via email if your interested. it fits an ls1 lt1 whatever maf you can find onto your car. so if your up for it drop me a line. its not a true beta anymore but we would like some durability testing done.

 

What did you use as the basis for your converter/translator? I used one of the LM2917's along with some schematics off of NS's PDF spec sheet and some specialty low tolerance caps and resistors for calibrating it. Works very well. Also some members here at TGO helped me out with schematics for protection circuitry and such.

As far as retrofitting the maf, it should be able to work with just changing the injector constant, MAF tables, and anything related to the mafs airflow. Youll be hit with a resolution penalty, but it should still work fairly well.

 

There is about 4-5% variance at low airflows that comes down to around 2% or so on the ecm side, plus whatever variances are in the maf and converter. Good enough, but not as good as SD can be. I wish I had more processing power and free time. Id make a system using both.

 

Hey Dim,

how did you finally implement the frequency to voltage transfer function? Do you calibrate the full scale of the LS1 MAF to 5 volts, or did you clip the resolution to 255g/s of the MAF?

I'm curious to see your final notes on what you came up with. If you recall, I sent you some stuff I had done, but never got around to building and testing.

oh, sorry for being off topic slightly. Way to go with the 3-2-7. Nice car all around!

 

I calibrated it to be around 5 volts or so at 12 kHz. Since I wrote the code for it I decided to have the capability to see flowrates above 255 g/s (up to 4096 g/sec). Also, I had no way of knowing what the actual output vs flowrate would be so it would be a shot in the dark to try and clip it at some point.

 

its a pic based micro with the ability to crunch expand etc a ls1 curve. you can curve it before the cumputer ever sees it. and you can also make full use of the sensors resolution on a 5v scale. its a nifty device for sure and is PC programable.

 

Sounds awsome... Any idea on the pricing when it does hit the shelves?

Being able to change the response curve has some definate advantages. Something that has a slight sort of logarithmic response with most of the voltage rise in the lower flows would be great for improving low flow resolution.

I was doing it on the cheap so the 2917 with its linear curve was all I could afford. Works well, especially considering the MAF and parts for the converter where less then 50 bucks.

 

its gonna be around $200 and it'll hit shelves sometime in the next 3 weeks. It's been designed by myself and a EE from a tier one supplier.

 

Not too bad, pricewise. Id consider picking one up. Thats a real boon as far as maf systems go. No more garbage bosch mafs.

 

we were trying to package that and the delphi maf for less then the cost of a replacement stocker.