Re-chipping Technical Question

[kevrobert]

On the basis of selecting a suitable EPROM to control the fuelling on my modified 924s and once again to gain horse power in the cheapest way possible am I right that with a 28 pin chipboard I can then choose to run any chip which I feel will suit the horsepower requirements of my vehicle... re utilizing a standard or modified EPROM chip from say a 944S an S2 etc.. as I believe the chip is only controlling the injector pulse rate, ignition timing etc..

[v2rocket_aka944]

no.
944S/S2 don't even use the same generation of DME as your 924S or any 8-valve 944.
the chips are not compatible and even if they were the ignition and fueling targets are significantly different between the engine models.

save your lunch money and buy the Lindsey NA-tune MAF kit...it's the best $600 or so you could ever put into your 944, seriously.

[kevrobert]

Originally Posted by v2rocket_aka944

no.
944S/S2 don't even use the same generation of DME as your 924S or any 8-valve 944.
the chips are not compatible and even if they were the ignition and fueling targets are significantly different between the engine models.

save your lunch money and buy the Lindsey NA-tune MAF kit...it's the best $600 or so you could ever put into your 944, seriously.

I understand that however if its only controlling the fuelling and timing curves I need some technical info as to why it will not work?? and its $600 against a $50 chip which may gain me just as much horsepower and how about using for ex a Motronic 1.0 E30 M3 Chip

[kevrobert]

Just to clarify a little more my NEUMAN camshaft pulls to a theoretical 7800 rpm (engine permitting!) at the moment stock rev limiter kicks in at 6250 so with for ex an E30 M3 modified chip the redline is increased 9% at 7650 up from 7000 (if the crystal oscillator is setup the same on the Motronic 1 cars then presumably ill see a raise of 9% upto 6800 rpm.) now potentially for $50 I am going to gain more HP than the 5-10% for a $600 outlay on the lindsey MAF..of course really I need the augtronic ECU , MAF and plug and play kit but then im looking at $2000. The fuelling requirements may or may not be more than I need from the M3 chip however I should be able to pull that back with the FQS and adjustable fuel pressure reg and spring tension on the AFM.

[v2rocket_aka944]

you need to look at ECU tuning 101.

timing and fuel settings are engine-specific - nothing about the design of an 80s M3 is remotely transferrable to an 8-valve 944 (wedge head, not much different than a 1950s small block chevy), 944 has much larger bore which affects the amount of timing needed, different displacement means different fuel requirement...then you get into manifold tuning differences which affect both fueling and timing...and so on.

as far as using a 944S/S2 chip in an 8-valve DME, if it were even doable...while the fueling might be "sort of close" the 16-valve cars use around 10 degrees less ignition advance across the RPM range because the 16v combustion chamber design is lightyears better than the 8v design. taking 10 degrees of timing out of your 8v would make it a dog...simply raising the rev limit does not make power by spinning the engine higher.

there is NO chip made by anyone, that will give anywhere near as good of results as the MAF conversion, period.

[DannoXYZ]

Look at dyno chart of 944 engjne. Torque peaks in mid-range and drops. HP peaks soon after that, and drops off after 6000rpms. Revving higher will just get you less and less power.. Actually, fastest acceleration occurs when shifting at 5000rpms to straddle highest torque range.



Fuel and ignition is only to optimise combustion of air after it's been sucked in. Max power occurs around 13.5:1 AFR on 944 NA engine. Any more or less fuel than that and you lose power. Ignition is to be optimised for octane-level of fuel you're using. Here's sample of maps for 85.5-88 944 NA engine. Each and every data cell must be optimised for airflow pattern through that particular engine. Any changes in fuel will lose power. Absolutely zero chance any other engine will have exact airflow at 25% throttle and 3000rpm, or 50%/4000rpms or 75x5000. Therefore absolutely zero chance any other engine's maps will be better, zilch!




Trick to more power? Get in more air and make it go bang harder. Want E30 M3 power? Then modify engine mechanically to flow as much air as E30 M3 first, then optimise fuel & ignition to match that airflow. Most effective mods on 944 NA starts on inside:

- larger big-bore pistons will suck in more air per stroke. Then you can inject more fuel to match. +15hp
- high-compression pistons give bigger bang per combustion event. +10hp
- stroker crank, again more air per stroke. +15hp
- larger valves with fully-radiused seats, ported head +10hp
- custom cam to tie all above together, +10hp
- Rogue MAF upgrade with programmable maps +10-15hp

Requires dyno-tuning to develop custom fuel & ignition maps for all above on your particular engine in order to extract that extra power. Factory chips will actually make less power than stock with this configuration. NO other engine's maps will work! Even two different bone-stock 944s will end up with different maps after dyno-tuning for maximum power due to production variations and different levels of wear.

I recommend reading at least just the following before modifying your car.

Internal Combustion Engine Fundamentals - Heywood 1988 McGraw-Hill
Engineering Fundamentals of Internal Combustion Engine - Pulkrabek 2003 Prentice Hall
Flow and Combustion in Reciprocating Engines - Springer, Arcoumanis, Kaminoto 2009 Verlag Berlin Heideberg
Performance Tuning Theory & Practice - Four Strokes - Bell 1981 Haynes
Tune & Modify Automotive Engine Management Systems - Hartman 2004 MBI Publishing

[DannoXYZ]

I used to program a chip for 944-Spec racers (Paul may have posted dyno chart somewhere). It required using +100 octane fuel full-time and got +5bhp over stock. There's only so much you can do with factory air-flow volume. You need to increase air-flow volume first in order to increase power. Notice how 4-valve head on 944S has very similar power to 1st-gen E30 M3? Upgrade your engine with 4-valve head first, then you can use 944S chip-maps in your car. Otherwise, you'll end up with less power than stock because chip-mapping must match specific airflow patterns of that particular engine.

[kdjones2000]

Danno, are you saying that Paul cheated in 944 Spec? You are not supposed to be able to chip your car in that series.

The shame, the shame...

[DannoXYZ]

Depends upon the year, rules changed from year to year. They go back & forth between allowing balance-shaft removal (+2.5-3.0hp). For a while, custom-chip mapping was perfectly legal. Then there was contention over "original chips" because you can erase "original chips" and download your own custom maps to them. Also perfectly legal was using any aftermarket standalone EFI system you want as long as it fits inside DME box. I made a few of those as well using Mega/Microsquirt or LinkECU motherboards.

[wildcat077]

Are you saying you managed to fit a Link ECU into a Bosch DME box ?
Doesn't the Link run off a crank sensor sprocket !

Just curious ...

[DannoXYZ]

I have Link G1v4 that's programmed to use bone-stock speed/ref. sensors. No installing additional sensors needed! Uses stock TPS and ECT. Basically true plug-and-play ECU that plugs directly into factory DME connector. Has built-in MAP sensor, so you just T vacuum-line to the KLR's boost-sensing line on 951s or run line out to intake-manifold and T off FPR line on 944 NA.

Similar to this Megasquirt conversion. Has benefit of AFM-conversion to MAP/MAF at same time.