View Full Version : Blow-through vs Draw-through 803 maf
jjjjjjj
03-12-2015, 02:37 PM
I have a very old obd1 AA turbo setup with the 803 maf in draw-through configuration. It seems there is a lot to be gained by moving to a blow-through setup as far as accuracy is concerned.
What, in theory, would need to be changed if I was to "rearrange" my current setup to blow-through venting to atmosphere vs recirculating like I am now? I have also read that the 803 will work either way but it will max out... I'll barely crack 400whp with my current turbo so this shouldn't really be an issue.
I could see using the 803 or even 540 maf as a good, cheap, pnp option for some people without huge goals if the tune was available, no?
e36ALPINE
03-12-2015, 02:57 PM
"I've heard" other platforms that have things such as "lift throttle enrichment" and "tip in or tip out" tables. I would have to look at my Romraider maps to see if those are available to change.
rowleym
03-12-2015, 03:09 PM
OBD1 we have acel enrichment table 4x6
You lose significant amount of head room if you switch to blow through. And supposedly some units arent meant for it. especially if they come in a plastic housing.
Ford slot style maf's are great for this, and thats currently the approach that every single stock dme tuner is using. AKA HPX blow through.
But we can use the actually stock ford sensor for like 15$ but with less headroom. This is what I will be trying.
jjjjjjj
03-12-2015, 03:43 PM
Yeah, I was thinking it would have to stay in the 3.5" housing which on second thought would be a huge pain because I'd have to modify quite a bit on the charge pipe... Making it useless for resale lol
Will probably end up selling most or all of my AA kit when the time comes to upgrade, I got a super deal so will just pass it along.
Using a $15 maf sounds amazing if it can be adapted!!
rowleym
03-12-2015, 03:54 PM
Absolutely can be adapted, it's just going to max out at around 400whp in a 3" pipe. 3.5" like 5 something.
But I think I'm going to give it a shot? If not, I can always just drop in the hpx MAF that's the exact same thing, simply modified. I bet they just add a resistor.
jlaudio982
03-12-2015, 11:15 PM
The HPX and VMP mafs are actually modified ford parts. What they do is open the maf and use a high powered laser they etch/burn two carbon resistors inside the sensor essentially changing the curve.
- - - Updated - - -
If you send PMAS a stock ford maf they can put any curve on it you need. Cost is 80 bucks but turn around time takes forever.
rowleym
03-13-2015, 06:57 AM
Cool beans! Good to know. Definitely the route I am going to take, but I will start with the oem piece for testing before I bite the bullet! Hopefully I can make enough power in a 3" pipe...
jjjjjjj
03-13-2015, 10:39 AM
I'm in for this. Maybe can get a few together for developments purposes
rowleym
03-13-2015, 11:03 AM
I'm very confident! With most things so far in my life, if I make it my goal to figure it out, I will. It's now simply a matter of how long will that take :) but it's the only thing holding me back from having a boosted car in a couple weeks. So that's one hell of a motivation, and not only that, but a local tuner with a dyno, that has figured it out(and he has lots of customers that I contacted him that vouch for him.) that is willing to help me. I feel that's one of the most important things!
jjjjjjj
03-13-2015, 11:50 AM
Yes, having someone local is a huge help. Have a friend of a friend near me who is supposedly an expert in tunerpro on other cars so I'm waiting until I have something in the works before I bother him! I'd like make a tune to share for an 803 based setup and a new setup hopefully based on that ford maf so I can upgrade.
Extreme budget limitation is my motivation.
rowleym
03-13-2015, 12:09 PM
^me too! I don't make much money at all. Still in my second year of apprentice, and I'm paying for my girlfriend to go to school, and I just bought a house and shop last fall(when I was 19) so funds are pretty tied up, and I don't like working over time. We have mandatory 50 hours though the last two years.....
rowleym
03-13-2015, 12:12 PM
Also, that expert should come very handy! Other platforms use tunerpro, and there is a lot of neat features. And a lot of things that we need to setup yet, for load scaling and changing injectors etc instead of having to manually edit all parameters that are effected with k value.
And we need to use the knock sensors! I'm not sure how great they are.
rowleym
03-13-2015, 08:00 PM
Tube Size Estimate HP range no extender 3" 250-300RWHP 3.5" 275-400RWHP 4" 350-500RWHP 4.5" 400-600RWHP
I have an oem 05 slot maf in a 3" tube. right now Its maxed out and I'm only 3/4 throttle @ 3000 rpms. I need a 4" tube in order for my maf to not max out, yet still retain the sensetivity of measuring air at low rpm's. Its not a good idea to run a 4.5" pipe on an engine that only makes 250whp. it can cause poor drivablilty. a stock 05 maf can be found @ a junkyard for 25 bucks, then get a MAFiA for 75-100 bucks (depending where you buy it), and for 100 dollars total you'll have a maf that can measure as much air as you need it to.
Quotes from some interneting ive been doing.
In my present application, with the sensor installed (http://www.corvetteforum.com/forums/#) as a blow-through set-up in a 3" tube, the standard 05+ Ford sensor, when extended via additional hardware (a 10 k resistor) should have the range for 400-450 RWHP. Extended range sensors are also available that can support over 600 RWHP.
The stock m3 bin reads 1127 kg/hr at 5v, and the ford slot style maf reads 1260kg/hr which is about 5 lb/min difference in flow. aka not a whole lot different than ours. Does this mean we can simply add a resistor and re tune for modest goals? Or is the ford maf have better resolution of some sorts and takes better to mods/scaling? Otherwise I might end up buying the ford maf, trying to max it out, trying to modify it, and if all else fails I will get one sent in to be modified.
bry195
03-13-2015, 11:42 PM
Tube Size Estimate HP range no extender 3" 250-300RWHP 3.5" 275-400RWHP 4" 350-500RWHP 4.5" 400-600RWHP I have an oem 05 slot maf in a 3" tube. right now Its maxed out and I'm only 3/4 throttle @ 3000 rpms. I need a 4" tube in order for my maf to not max out, yet still retain the sensetivity of measuring air at low rpm's. Its not a good idea to run a 4.5" pipe on an engine that only makes 250whp. it can cause poor drivablilty. a stock 05 maf can be found @ a junkyard for 25 bucks, then get a MAFiA for 75-100 bucks (depending where you buy it), and for 100 dollars total you'll have a maf that can measure as much air as you need it to. Quotes from some interneting ive been doing. In my present application, with the sensor installed (http://www.corvetteforum.com/forums/#) as a blow-through set-up in a 3" tube, the standard 05+ Ford sensor, when extended via additional hardware (a 10 k resistor) should have the range for 400-450 RWHP. Extended range sensors are also available that can support over 600 RWHP. The stock m3 bin reads 1127 kg/hr at 5v, and the ford slot style maf reads 1260kg/hr which is about 5 lb/min difference in flow. aka not a whole lot different than ours. Does this mean we can simply add a resistor and re tune for modest goals? Or is the ford maf have better resolution of some sorts and takes better to mods/scaling? Otherwise I might end up buying the ford maf, trying to max it out, trying to modify it, and if all else fails I will get one sent in to be modified.
supposedly making this mod on the oem maf doesnt work. I have nothing tangible to provide you with but I did a little research and from what I remember the oem maf is too sensitive for blow through in a turbo application.
the flow voltage relationship is very non-linear and different from maf to maf.
maybe create a test fixture. an old 1" id air cylinder with a maf in the middle (use math to comp for 1" versus 3"). pump the rod at a given speed and you will have a fixed displacement. create a table correlating air velocity to voltage. then add back pressure to the table. this should tell you if a maf is suitable to play with resistors.
or pick up a used dwyer flow meter and use a compressor.
its possible to stretch a maf out or condense it with resistors but you still have a few other things that will make it difficult. once you create a test rig you can tell what will work.
rowleym
03-17-2015, 09:01 AM
http://www.v6power.net/vb/archive/index.php/t-49130.html
yup. Went and bought myself a MAF and some resistors. I think the potentiometer is a great idea.
jjjjjjj
03-17-2015, 06:12 PM
http://www.v6power.net/vb/archive/index.php/t-49130.html yup. Went and bought myself a MAF and some resistors. I think the potentiometer is a great idea.
Please do. In for results even if I am 3-6 months away from doing such things!
bry195
03-17-2015, 09:53 PM
remember mafs are not linear. when they are loaded with a resistor in a vacuum the curve condenses evenly with the non linearity. in the real world they dont. its a trade off but you may strike gold. 0-10k and 10 turn will help too.
bry195
03-23-2015, 11:17 PM
I picked up a 30 dollar honda civic hitachi maf. I really just wanted to fill the hole where my old miller maf was mounted and it was cheaper than a block off plate. it has the exact same mounting, footprint, seals....it looked identical to the miller slot style maf in every way other than the miller has a custom machined connector receptacle for the bmw connector. if I get to where I need more than the MAP sensor maybe I will play with a resistor or 2.
Butters Stoch
03-24-2015, 03:10 PM
Blow through much better. No question about it. Tho I have driven a 600wheel draw through AA 4094 car. It was nice .
MrInfinit3
05-06-2016, 04:46 PM
Any updates to this?
I just have issues paying more for "XXX" MAF then I did for the Piggyback/tune and injectors combined lol
Powered by vBulletin® Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.