daly944

I have a 1987 944na that i'm designing a new intake setup for, and i am very interested in the map setups that speedforce racing sells. (www.speedforceracing.com) What exactly do i need to do to install a map setup? Anyone have any experience with one? THanks for any advice/help
Brendan.

Danno

"Anyone have any experience with one? "

Yah, we've got <a href="http://www.gururacing.net/History.html" target="_blank">plenty of experience</a> with those MAP sensors! First, you'll need an air-temp sensor so your DME is happy and makes the proper air-fuel corrections. While adjustments for air-fuel ratio for stoich. mixture isn't that far off, there is a significant enrichment beyond stoich. under cold-start conditions. That is, it can trigger your DME to run 16.3% richer than normal.

Then you'll also need the calibrations for an NA AFM. The idea is to program the MAP-sensor to mimic the AFM as closely as possible. Measure the closed-AFM voltage, then the fully-open AFM voltage. Configure the MAP-sensor to generate values that matches and that's it! Of course, you'll need to tune it on the dyno to dial in all the fuel-zones. Here's a blank worksheet: <a href="http://boards.rennlist.com/upload/AFMLINKZoneWorksheet.gif" target="_blank">MAP-sensor zone-worksheet</a>.

The calibrations for a 944NA is completely different than the 951. You won't ever go beyond zone-575 in an NA, so you'll want to make that the max 5.0v output instead of 2.63v like it is on the 951. Again, best to put a stock car on a dyno and populate that table with numbers from the stock AFM, then program those into the MAP-sensor.

Now we had investigated making a 944NA MAP-kit, but decided that the results weren't worth the effort or expense (gain 6-8hp in high-end, lose 5-8hp/10-15lb•ft in low/mid-range). The benefits of correcting <a href="http://www.gururacing.net/images/Dyno020706-TQcompare.jpg" target="_blank">wildly-incorrect air-fuel ratios</a> just don't exist in a 944NA like it does in a 951. The NA's fuel-curve is close to spot-on as it is (a little rich).

Rather than spend so much money and effort for minimal gains, we're working on a kit that will give 944NA cars an additional 100HP!!! Now THAT, is worth investigating... heh, heh...

pete944

[quote]we're working on a kit that will give 944NA cars an additional 100HP!!! <hr></blockquote>

You're such a tease.

PCinDC

Danno -

100 HP?!?! I'll asume comparable torque increases....

Hoping it's not going to cost me $5000...

Timelines? Will we possibly be able to do this as a nice winter project before putting the car on the road in the spring?

Hoping so!!!!

david fracolli

Danno, what about on a modified car? I am having problems controlling the air/fuel ratio with the cam that I am running.
Dave Fracolli
85.5 944

art

Why would you lose power in lower RPMs with the MAP sensor. If you can program the fuel values correctly I would think there would gains at the lower end due to not doing work to move the flap.

Art

art

Why would you lose power in lower RPMs with the MAP sensor? If you can program the fuel values correctly I would think there would gains at the lower end due to not doing work to move the flap.

Art

david fracolli

I was wondering the same thing?
Danno?
Dave Fracolli
85.5 944

Danno

"100 HP?!?! I'll asume comparable torque increases.... Hoping it's not going to cost me $5000..."

Yup, +100hp/+100lb•ft over stock. Most likely will be less than $4k... we'll see...

"Why would you lose power in lower RPMs with the MAP sensor. If you can program the fuel values correctly I would think there would gains at the lower end due to not doing work to move the flap."

Remember that managing fuel comes AFTER managing airflow. Programming fuel-curves is only in response to the air-flow patterns you've created. In a Turbo, the air-flow pattern is easy, you turn up the boost 30%, you add 30% more fuel fine!

NA cars are not as simple as turbos. There are two factors we need to consider, flow-velocity and harmonic induction tuning. The loss in low-RPM torque is actually due to the loss of restrictions which actually AID flow-velocity and chamber-filling at low engine speeds (the flapper-door acts as a venturi). Also since the engine is an air-pump with reciprocating cylinders, there are numerous harmonic pressure-pulses going through the system.

You have exhaust-pressure pulses going through the headers. And with the 4-2-1 header, you have the 1&4 and 4&2 cylinders dumping on top of each other creating a double-pressure wave. Between the pressure-waves, you have a double-vacuum wave. At the optimal RPM, this vacuum wave flows past the 2-1 joint and helps scavenge exhast from the other cylinders.

However, at other RPMs, it's the double-pressure wave that coincides at the header collector as the exhaust-valves are opening for the other pair. This pressure then pushes exhaust back into the combustion chambers! This typically occurs at 1/3 to 1/2 of the power-peak's RPM.

This is where flow-velocity comes into play. Think of it as an integration of the harmonics at each and every single RPM. This will determine the exact volume of air that's ingested at that RPM. By enlarging the intake and removing restrictions, you slow down the column of air. Inside the chambers, this results in less pressure and less force to CRAM more air into the chamber as the piston rises for the compression-stroke even though the intake-valve hasn't closed yet. This lower intake velocity is also detrimental at the 2000-3500rpm range where you have exhaust reversion as well. This means more of the intake-charge gets pushed out by the exhaust than before.

What we really need on the 944NA cars is to upgrade to the later types of technology rather than just extending the existing systems. Upgrading to things like variable-valve timing, variable exhausts and variable intake length & volume will allow you to tune the actual harmonic frequencies where these back & forth pressure pulses are occuring. Then you can place the bad reversion RPMs in ranges that you'll never use in your car... like 9000rpm.

Without those mods, you have the usual conflicts of interest in opening up the NA intakes similar to free-flow exhausts. You get more high-end flow for power, but you sacrifice just as much in low-end torque. While this may be fine for race cars that only use the 5000-7000rpm range, on a street car it will be more frustrating to drive. Sure, the MAP-sensor can be programmed to meter fuel accurately for your new air-flow patterns, but is that the pattern you want; more high-RPM flow at the expense of the low-end?

"what about on a modified car? I am having problems controlling the air/fuel ratio with the cam that I am running."

Send me your dyno chart, I burn you a chip to fit your modified configuration and that's it! Most likely you'll need a 4-1 exhaust header to work with that cam too. Instant adjustability is great and all, but how many people change their configuration often enough to justify the cost? Especially considering you'll need to pay for dyno-time each time you want to make an adjustment.

M758

So Danno,
What is your take on the following NA Set-up

87 924S motor Stock
Completly Stock intake system and paper air filter (inlet in fender still)
Stock 4-2-1 header.
2.25" Exhaust pipe No Cat, No Muffler.
Stock DME
Stock FPR & Injectors
91 Oct Pump Gas
Typical RPM Range 3500-6200

I went to this set-up on my race after I cracked my cat pipe and removed for one race. It definitly gave me high rpm power and I decided to keep that like that.

I have not dynoed so I don't know where i am with repsect to A/F Ratio or low end hp.

Do you think this decient set-up for track motor?
Should check A/F Ratio?? Think I could be running lean??

Mark Parker

Danno; I don't want to beat you to death over this, but your post has really got me wondering. If I understood you correctly, the barn door in our AFM is , in some way, beneficial to low and mid range power as it serves to increase airstream velocity at the cost of volume. Why then are the hot wire meters so highly touted for their free-flowing characteristics, or are they in fact detrimental to low end performance ? Also, I thought at first that you were strictly yankin' our chains when you talked about "100 hp gains" with similar torque increases. But as I read what you said about moving into new technologies like variable intake and exhaust volumes, it occured to me (doh) that you are dead serious. Can I venture a guess that you're working on some kind of dual plane intake for our sleds ? Garwsh,,I'm gettin a little beefy at the very prospect !! Thank goodness for guys like you who have such a passion for cars like ours. <img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />

Douglas_T

It all sounds very interesting! Thanks for the info!

Danno

"the barn door in our AFM is , in some way, beneficial to low and mid range power as it serves to increase airstream velocity at the cost of volume."

Yup, the AFM in the 944NA is about the same size as the 951, which can flow about 2x as much air. In that case, it does become an obstruction to quick total-volume flow at high-RPMs. The 1.5psi drop we see with the AFM in place works out to about 20-25hp. Since there's no harmonic induction tuning in a Turbo, we don't have to worry about low-end torque in removing the AFM.

"Why then are the hot wire meters so highly touted for their free-flowing characteristics, or are they in fact detrimental to low end performance ?"

If you dig up Carl's thread where he dyno tested his S2, he got more power from his stock S2 than a lot of others with MAF upgrades. This shows that production-variations alone, creates a wider range of power outputs than the gains from a MAF upgrade (typically 7hp in S2, around 5hp in 2.5l cars).

Free-flow MAFs are great if they are designed into the system from the beginning. That way, the air-box contruction, intake-runner lengths and plenum-volume, cam-timing & duration, exhaust-headers and muffler-types can be specified with the MAF as part of an overall system. Good example is in going from the S2 to 968 engines. The MAF gives high-end flow, yet VarioCam takes care managing optimal valve-timings over a broad RPM-range so you don't have to sacrifice low-end torque. AND, high-RPM power is increased at the same time.

Now a similar, but not as effective mod CAN be done on non-VarioCam cars. You would open up the intakes and exhausts in the head for high-RPM flow. Then you would advance the intake-cam to move the torque-peak lower to regain some of that lost low-end, but not so much that you lose all of the high-RPM power as well. The result will then be a torque & HP curve that's a little higher than stock overall, rather than a higher just at the high-RPM end.

It's really tough to extra power from an NA engine with bolt-ons since the most effective upgrades are from the inside out. This is typical hot-rodding that's been developed over decades with 2-valve engines. Start with the pistons and increase compression. Using only the highest-octane gas, you can get away with 11.0:1 on a street car. Then polish piston tops, the combustion chamber and finish the head with 5-angle valve-job. Back-cut the valves and port-match the ports to the manifolds. Finally, top it off with a cam with a little more duration than stock, but with a quicker ramp-up rate. Advance the intake-closing about 4-8 degrees to get some low-end torque and you've got quite a monster! Now we're looking at a 15-25hp increase without losing any low-end torque.

Due to the chemistry and thermodynamics involved, it not really possible to extract more than about 85-lb•ft/liter•bar out of an internal-combustion engine on gasoline (F1 cars aren't getting much more torque/ltr than this). What you can do, is make this torque-peak as wide as possible over the entire RPM-range. Or if you've got a race car, make this same torque in as high-RPMs as possible . This will let you more power with the same torque. You can also use lower gearing to get more torque at the wheels as a result of higher revs.

Danno

"What is your take on the following NA Set-up

87 924S motor Stock
Completly Stock intake system and paper air filter (inlet in fender still)
Stock 4-2-1 header.
2.25" Exhaust pipe No Cat, No Muffler.
Stock DME
Stock FPR & Injectors
91 Oct Pump Gas
Typical RPM Range 3500-6200"

That looks fine. A K&N filter element may help somewhat. If the 944spec rules allow, you can get an adjustable cam-sprocket to fine-tune the torque-peak to place it at the range you're using the most. This can be adjusted on a track-to-track basis to give your car the best acceleration coming out of the corners that'll save you the most time down the straights. I still need to get you a chip too.... but you'll need F.R. Wilk's pre-'85.5 chip-adaptor to use it on the early DMEs.

Paul Bloomberg

M758,
Are you using the early DME with the later injection on the 87 motor? Or did you use the later DME?
Danno,
I wanna chip too!!! : )
Paul