I am coming very late to this discussion and I am not any kind of F car expert. In the world of Honda where I dwell, the three most important tools are the Air/Fuel ratio meter which gives a real time look at actual fuel mixture condition, the adjustable fuel pressure regulator which is the simplest method of effect mixture rich/lean and a fuel pressure guage. All three pieces are readily available through typical dealers for about $50 each. I am sure that these could be adapted for use in F cars. I have found even with what we think is a "massive" increase in air flow, a realtively small increase in fuel pressure through stock injectors will cure lean mixture. Scott (who works with Ernie)
The plan is to replace the air boxes with stacks and replace the MAFs with a MAP. Maybe run tall stacks thru a hole in the lid or short stacks like Andy. With the current setup 1.25" of lift is needed in front. With lid closed, you can't tell it unless you're looking for it.
So in matching the 2.5 tables to the 2.7 tables I discovered something cool. Motronic 2.5 and 2.7 have a table from idle to redline for setting how much time the coils charge. Heckofa variable to be able to control. Want a bit more voltage? M2.5 and 2.7 are *not* tapped out in OEM trim. Oh, Plugzit will be getting Stooge v0.3 tomorrow morning. He can tell everyone more of what that chip will do.
Now you are talking! If memeory serves that's only 65hp less than Goth 355 @ the wheels! Looks like 348 guys may not need no stinking crappy 5 valve heads with lamo guides????
ND, What will more voltage do at the coils assuming the mixture is burning fine? Don't you only need more volts if the amount of fuel is increase quite a bit?
Right. It would only make a small increase in burn efficiency at the expense of shorter coil and plug wire lifespan. ...but...it's there. We *could* bump it up if we wanted (say, for a track day chip). No one says that you have to drive all of the time on the same set of chips.
You know what we really need to get ahold of? A set of 355 2.7 chips. Then we can see what the 355 is doing through out the rpm range. I think that will help take a whole lot of the guess work out of this.
Just posted "where's Gothspeed"? I'll bet he'll help! Who's guessing? Aren't we simply taking a systematic approach to a complex problem with certain waypoints in building a matrix for successful results?
A good idea, but then we'd have to account for the different fuel pressure of the 355, the different fuel injectors of the 355, and the different displacement...plus the different fuel mapping tables. Of course, I say all of that and watch the final Stooge chip be nearly identical to a 2.7 355 chip like you said all along! Life has a sense of humor, I guess!
Works for me! I'd truly like to compare the maps. I'd graph them and post them here just for the heck of it. Oh, I just need one 355 chip, by the way. They are identical between ECUs. I can scan it and overnight it back. Same maps, so no need to scan both chips from the same car. A 348 non-spider 2.7 chip would also be nice to have/scan. Say, something between 1990-1993. Any 348 Competizione LM owners want to let me scan a chip for comparisons and graphing?!
The charge time is about getting the coil to saturation, once the coil is saturated, no additional time will improve the spark voltage/energy. In fact, extra time will actually hurt the spark a bit because the coil will heat up and resistance of the wire will go up. Probably not a good idea to mess with.
From the data, the Motronic 2.5 and 2.7 OEM coil charge table varies in duration based on battery/system voltage and RPM. Lower RPMs get a *shorter* charging time per the OEM table. While lower system voltage causes the table to give a longer charging time. Where it gets interesting is that the table does not max out the charging time for normal and high voltage conditions at high RPMs.
That does seem odd. The scheme the aftermarket ECUs seem to use is simply a fixed time, which makes sense…although I’ve never put a scope on the signal, they may very well be doing more than the inputs lead me to believe. Strange, I wonder what the reasoning could be…… It looks like the tune is getting close, v3 may be a winner.
Right. Here's a screen shot of the coil charging table. Higher hex values mean longer coil charge times. Notice the E4 values for the low voltage, high RPM conditions...and compare that to the smaller values when voltage is normal or high when the RPMs are high. (RPMs on left going vertically, Voltage values on top going horizontally) Image Unavailable, Please Login
Im guessing they specd a coil with pretty low resistance in the primary winding so it could generate a good spark even in a low voltage condition. But at higher voltage, it just flows too much current and gets too hot. They reduce the time trying to achieve basically constant charge.
Cool! The new blank chips should be in by the time I get back from skiing, and it will be *easy* to bump up the hp from here on out. OEM=145 rwhp V0.1=205 rwhp V0.2=235 rwhp V0.3=260 rwhp We've got *lots* of room to bump up the t3 table (that's what gave you the +25 rwhp bump on V0.3 from V0.2). Life is good. Still getting lean symptoms, I presume?!
