Need help setting the advance table, rev limit etc on my electromotive ignition!!

[pjo046]

I am about to install an Electromotive HPV-3b ignition on my car. This is basically the same as the XDI2 but with lower resolution on the ignition advance table (8x8 on the HPV-3b).

My engine is a stock C3 (3.0 carrerra, 200 fwhp, 8.5:1 CR), with headers and custom muffler. I will be installing a Bitz EFI-kit as well.

What should I set the rev limiter to on this engine? In other words, how high can one safely go with stock internals, if one wants to be on the safe side?

What is the recommended initial advance? (The advance below 1000 rpm)
If anyone has opinions as to what is the optimum ignition advance table, I'd be glad to hear it.

Since I only have 8 rpm points to use, what would be the best set points? I am thinking 1000, 1330, 1660, 2000, 2500, 3000, 4000, 6500? Or?

All inputs are appreciated, as I am a true novice on this field.

[pjo046]

Btw, I am glad to hear from everyone, as this is not Electromotive-specific.

[KTL]

The 3.0L engine has decent rod bolts and can withstand more revs than a 3.2. A 3.2 with the lesser rod bolts has a factory rev limit of 6250. However, you need to decide if revving yours further is beneficial in terms of the powerband. I know of many stock 3.0L that "run out of breath" near 6000 rpm. However if you've messed with the mixture, removed the cat, installed a sportier muffler, possibly installed different cams, you can see the benefit of these modifications in the higher rpm range for the 3.0L CIS engine.

I think you'd be safe with 6250. I have a couple friends who wind their 3.2 Carreras to 7000 all the time for years at track days and they've not zinged the engine yet.

[pjo046]

I believe I have read that the C3 makes it's peak power higher in the power band than the various SC 3.0. If so, it might be beneficial to go as high as possible within safe limits. Perhaps 6500 rpm would be ok? 7000rpm would be pushing it?

My exhaust is more or less as free flowing as it can get since I have headers and a 2 in 2 out muffler. The fuel injection will be optimized with the help of Bitz EFI (Megasquirt), and a LC1 wideband lambda.
Perhaps in the future I'll increase the compression ratio and add better camshafts (when doing an overhaul on the engine), but as for now the modifications I have/are about to install will have to suffice because of lack of money.

[pjo046]

No one with input on the advance table? It is 8x8 with 8 Kpa points (30-100 Kpa in 10 Kpa increments) as load indication, and 8 rpm points as noted earlier. The unit extrapolates linearly between the set points.

I guess 35 degrees is the maximum advance I want at full throttle? (100 kpa) And this should come on by 3000 rpm? And from there and on it should gradually decrease towards 6500 rpm?

[KTL]

Maybe post this in the engine rebuild forum? There's some extremely experienced people who frequent there more than the general tech forum

[psalt]

My advice would be to get the factory curve (max 38 BTDC @ 6000 rpm, but check) for your engine and mimic it with your initial settings. You will see there is a knee in the curve around the torque peak when cylinder pressure is highest and the chance of detonation is highest. When setting up an advance curve you want to focus on max advance, initial advance is less important and usually dictated by distributor limits or emission tests. An engine need no advance at idle, TDC is OK, cold idle may be improved at 5 to 10 BTDC. The basic procedure is to advance the timing until detonation occurs or the torque falls off, but you sound like you have no experience, so I would suggest being conservation until you can get some help. The 911 is a knock limited design, meaning you generally run out of octane and run into detonation before you over advance and output drops. Many things effect how much advance you can run, compression, air temp, oil breather, engine temp, octane, valve timing, port size, etc. and no one can tell you the best curve in an internet post. For example, in the 3.0, Porsche chose in raise the compression for efficiency, narrow the ports to lower the torque peak, while lowering the fuel spec to 87 CLC octane, which resulted in a 25 BTDC max advance for the later US 911SC. This engine requires a different advance when you change the intake, torque peak, exhaust heat and fuel spec.

The US 911SC has a fuel pump cut off at 6700 rpm, the Euro model an ignition rev limiter of 7000 rpm ( a difference dictated by the converter).

Paul

[pjo046]

Thanks for the reply!