Manning

OK, this has been discussed before, and many have said that it isn't worth doing.

I was just at Grassroots Motorsports site, and they have a current E30 M3 project going (yes I really like that old BMW). They added a MAF kit from Split Second, which is for the most part the same kit Huntley sells (in fact split seconds site links you to Huntley's). They gained 12 hp and 9 ft lbs of torque. Now I know that you wind up paying around $100.00 per horse, but the potential for additional tuning and mods is expanded as well.

http://www.splitsec.com
http://www.grassrootsmotorsports.com


No affiliation by the way.

TT

I agree, $100/hp is not really cost effective for a 944. A friend and I decided to see what it would take to adapt a MAF to a VAF vehicle. I ponied up my 944 for the modification and we started back around the beginning of July. The goal was to outfit the car with a MAF on a budget in which if it did not work I would not be heartbroken to throw the pieces away. This was a part time project, but I hopefully completed all the major hurdles today. Here are some pics of the system.







The MAF is a Bosch hotwire sensor that outputs a voltage signal. I installed a thermistor into the MAF that has identical characteristics to that of the VAF. The output of the MAF goes to a box we built with an embedded micro programmed to convert it to the equivalent VAF signal.

I've driven about 400 miles using the setup so far in the hot weather here in MD, but I keep the old air box handy in the car just in case. The only noticable change so far is a difference in throttle response and a large increase in the noise from under the hood (a loud sucking sound).

It can't be getting much if any extra hp at this time (it looks completely like the VAF to the motronic) but I am going to add an adjustable FPR, increase fuel pressure and adjust the MAF/VAF curve accordingly. I have lots more tuning and testing to do. Eventually it is going on a dyno for final testing and tweaking and a comparison between the VAF and MAF (takes about 2 minutes to swap the two).

Our next project is to fit a GM MAF (frequency output) to my friends BMW 318is. So far it has been very interesting and I have learned alot about Motronic operation along the way.

Magnus

Very interesting post TT! I have also been thinking of doing this conversion. I was originally thinking of doing the signal conversion with analog circuits but since you made work with a micro controller that must be the way to go.

I have some questions about your setup.
1. What MAF are you using? Bosch number 0280XXXXXXX ? Donor car?
2. Tell us some more about the electronics that do the signal conversion?

Thanks in advance!
//Magnus

TF

I believe Pro Flow makes a MAF that will work on our 944 NAs. I e-mailed them several months ago but haven't had time to follow up. Just finished clutch and starting other stuff which took $$$. I think it was about $200 or so but not sure what else was needed but they have a unit that will work. I think Autothority uses their MAF. pro-flow.com is their site. I was going to call when I was ready, to get more details but won't get there until spring or summer. If anyone gets anymore info please let us know. I also believe it will help but many $$$/hp.

TurboTim

We just dynoed an 87'N/A(to get a baseline for our supercharger) with the Huntley MAF kit, headers, testpipe, Nology coil and wires and everything else you can imagine.It made 131 horsepower at the wheels.A stock car makes 125 at the wheels.$3000 worth of crap for 6 horsepower! BTW, with the mass-flow system, this car would fall through idle and almost stall everytime you let off the gas. I think the money would be better spent elsewhere.Our supercharger for example is an excellent choice for roughly $3000.As a matter of fact, our supercharger is awesome.On this same car that made 131 at the wheels, the power at only 3 psi is incredible! We did have to swap out the Huntley MAF sensor with our smaller unit because the idle was still falling through when you let off the gas.The good news is that our smaller sensor cured the problem and now the car runs as civil as a stocker but with alot more power.It litterally feels faster then a stock 951(makes 182 HP at the wheels).As you know we will be running at least 5 psi on our base system and close to 8 or 9 on our intercooled systems.We will have our final dyno results for the level 1, 2 and 3 kits this Friday for everyone to check out.I gaurantee that you will not be dissappointed!

Tim
86 951 http://www.speedforceracing.com

Dave

Tim, How 'bout a baseline run with that smaller MAF?

Mongo

Turbo Tim i ended up takin' a drive out to where your shop is off prospect...i couldn't find it. I just found a bunch of homes around there. is there a side street you are on? did i miss something? email me directions so i can come check out that supercharger i am very interested =)

email: pors944@earthlink.net

TT

The MAF is a Bosch 280 212 007 from a Volvo 750 wagon IIRC. The converter box is an HC12 w/internal 8-bit ADC and an external 10-bit serial DAC. The software just reads the MAF inputs and outputs the corresponding value from a table for the VAF output. Since I last posted this stuff I completed a rebuild of an '88 NA motor, installed the engine in the car, and have patched the Motronic code to remove the need for the converter box.

Cost for materials was $40 for the MAF, $0 for the converter (friend at work had an old HC12 prototype board he gave me and I pulled the serial DAC from stock), 20 cents for a VAF electrical connector from a VW Fox, $2 for a Saab air intake tube that interfaces to Bosch MAFs, $1 for a thermistor, $0 for the mounting hardware (I made it from scrap metal at work) and a bit of my time. This was a test rig only, the requirement was that I would be comfortable in throwing away everything after I finished without worrying about wasting money. The only extra wiring required was a dedicated 12V power line and ground for the MAF in addition to the VAF lines (VAF is 5 volt only). I used a separate connector for those so the whole thing swaps in and out with the old VAF/air box very quickly.

The Saab air intake tube is good in that it allowed for an easy mount of a K&N filter and still provides a length of intake sufficient to induce laminar air flow through the MAF. I have logged over 2k miles with the setup; 1k on the old engine and 1k on the rebuilt engine. I recently put the VAF back in because emissions tests were due (didn't want to cross that bridge yet).

The MAF output is very non-linear at low airflows and requires lots of averaging to eliminate the noise, I would assume that is why the large MAFs don't do well at idle. I have had no problems at idle or top end with my setup. I am currently working on my next project before dyno testing the setup to see the results. I will also be getting my hands on a current generation MAF soon; these have direction detection to eliminate false air readings.

Dano_944

Guys, guys, guys! Let's think about this: I'm reading that you are spending between 3K and 6K to modify a 3K to 6K car! What!?!?! I've said it before, I'll say it again: the output on a 944 stock N/A engine is as close to its's peak as you're gonna get. Period. If you've got 3K burning a hole in your pocket, and you want more speed and power, sell your car, take the combined cash and buy a 951, a 944S2, or go all out and find a clean 911. Modifying a N/A 944 motor for a couple of HP ( and I mean only a couple, 'cause that's all you'll get) is like bronzing a gold metal. No offense to Guru's like the guys at Huntly, Extreme, or any other shop. You guys are brillient in some applications. Derreck Huntly said it very well at the recent PCA Tech Session regarding HP and weight.... "you gain HP simply by losing weight". So lighten the car a little, start that Genny Craig program, and leave the N/A 94 motors alone. Just my 2 cents (which I'm saving).

Magnus

Thanks TT! Your answers will probably be very useful!

//Magnus

Luke

The Bosche Unit from the VOLVO is probably the same thing Pro-Flow uses!

Just need to be able to wire an arc2 up to it.

Manning

Dano_944,

Because it's fun and challenging. I don't really thing a 944 motor is at its peak and I bet Jon Milledge would agree. Granted the resulting car might not exactly be streetable (lumpy idle), but it will produce more power. Milledge claims to be able to produce a SCCA ITS legal engine that will produce 185 bhp. I am not sure if that is at the wheels, but if it is, that is 50 or 60 more than stock power at the wheels. That adds up to about 230 at the crank for a SCCA legal motor.

Yeah your going to spend an *** load of money to make one of these motors honk, but a lot of the tweaks that are usually addressed are bolt-on. Get into the really big money and you may get much more power, if only to prove it can be done. Flow, cc and port match the head, hot cam, better induction (like Milledges individual throttle body unit), MoTeC, lightened and knife edged crank, lightened flywheel (not for power gains) etc.

Again, it is a lot, and I mean a lot of money, but if someone wants the challenge and has the bucks, why not. NA's just strike me as more fun to fettle than turbos.

Mongo

Guys lets make it simpler...spend 2k of that money which is about how much it will cost for this MAF into a head; port match and polish and enlarge both intake and exhaust valves, regrind your cam to a .480 lift and voila. 185 HP right there.

Magnus

If you can build a working MAF-system for around $100 using used parts I think it can be worth it, even if you only gain a few ponies.

//Magnus

deni durrell

dano_944-
in light of doing the those $3-6k mods to a $3-6k car... I believe it's all about having fun and pushing the car further, regardless of spending the $$ (no offense intended). After all, the price i feel my car is worth is equal to the amout of pleasure i get from driving it. If I wanted to save money and have a "regular" people-carrying car, I would have bought a newer VW Golf, Polo or a Fox (i.e. non-performace minded). When a limit has been reached (whatever "limit" means - it's up to the driver of course)- It's time to get a 951 and keep going. Why not?! Life is too short. Right or wrong, it's difficult to reason with that stuff when all of us are passionate about tweaking our 944 NAs.