Tootie Pang

iTrader: (2)

I've done everything OEM possible to this 305 and it runs great now except for about 4,000 RPM and above at WOT the engine just goes flat.

I can rev it all the way up to redline in idle and it is smooth.

New/refurbished everything. (I mean everything)

Vacuum is 17 inches idle and near zero all the way up at WOT (exhaust is clear)

Fuel Pressure 37-45 in all conditions. No leaks.

Idle is smooth and stable 550 RPM.

Changed the plugs from new Iridiums to new coppers. New wires, properly routed, new distributor, etc, etc, etc.

I had the 771 D3's in there but they threw my BLMs off up to 160. So I put the Multecs back in and it runs great except for the high RPM issues. BLMs tend to be 115.

So now I look to the notorious Multecs. I remember reading here and there about how when they heat up, at high load, they can freak out. I ohmed them cold and warm and they all came out 15-ohms.

Can anyone share more information on this?

ULTM8Z

Do you know that the fuel pressure is holding at WOT?

Facotry TPIs are notorious for going flat above 4000 rpm... sure you're not simply expecting too much out of it?

Tootie Pang

iTrader: (2)

Yes, it's definitely not right. Before I cracked open this 28 year old motor, it would rev to redline at WOT just fine. And with the D3s just six weeks ago, it would rev right up. These TPIs will usually start choking around 4500. Say in first or second WOT, the RPMs are just flying up and then right at 4,000,stumble and the needle just stays at 4,000 RPM. The engine can't go up once it stars stumbling. It doesn't die or anything, it just stays right there. Sometimes it recovers and sputters up a bit more.

ULTM8Z

Sounds like you're going super lean or somehow losing spark energy out of the coil...

Thpugh The 115 BLM seems to indicate the ECM is having to remove fuel at least during non-WOT operation...

So you've verified fuel pressure is good at this WOT condition?

Tootie Pang

iTrader: (2)

Yep. 45 psi solid held WOT and about zero vacuum. Lean is what I am thinking. I keep reading nasty stuff about old Multecs so I should probably ditch them.

I ordered the yellow -710 D3's and an adjustable regulator. Maybe I can get this dialed in without a tune.


Maybe I should try bumping my timing from base to about 10?

ULTM8Z

My guess is you won't be able to tune for injectors with fuel pressure. I tried that on my friends car when his BLMs shot up to 160 with the Bosch IIIs and it didn't work. From what I've seen, high BLMs seem to be the typical response by the ECM to these injector swaps. Retuning the ECM is really the only way unless you some how end up with BLMs that are only a few points off from 128.

Bumping the timing at the distributor will add timing everywhere. Unless you change the base timing value in the tune to match it, but that would negate the increase. At that point you may as well just go into the spark map And target the increase to WOT... there's a table for WOT spark adder. But I don't tthink that will help this situation either.

Ideally a wide band O2 would really help nail down the problem.

Tootie Pang

iTrader: (2)

I think the manual FPR and bigger injectors may be a solution. The ECM doesn't know whats on the end of the injector connectors- it just fires the injector widths per a table and can only adjust them so far in either direction if the O2 reading is off. So if I'm hitting BLM 160, the ECM is out of adjustment and its still seeing a lean condition. If the -771s are only 17 lbs, then even at 48 psi they are still only 17.4 lbs (according to a calculator). 17/19 lb is 11% less and I don't know how much 1 (one) BLM unit changes the fuel delivery. Hoping I can dial it in.