I have posted about this before, but I have more information that may allow some of the gurus here to solve the problem.

The bottom line: HP is way below what it should be. I am getting on the dyno 106hp at the wheels.

The motor:

2.7 liter flat 6.
Headers
Modified E-Cam for carbs.
CIS runners and throttle body with Megasquirt EFI. (Tuned on the dyno.)
Pertronix ignition and multispark second strike controller
Mahle euro pistons and cylinders

I checked the compression and its right around 160 within 5%.
I checked the timing, at idle and all in at 5,000. (Kind of un-nerving to check.)
Spark is strong. New plugs.


Ok. Here's the new bit:

I ran an autocross this weekend. The engine was around 160 F at the start of the runs. The first and second run, the car missed and backfired right around 5,000 RPM.
On the third run, the miss completely went away. Same on the third run. My co-driver drove 4 straight runs and no problems. I even did a 0 to 60+ run all the way to redline without a single miss.

So, what was different? The engine temperature at the third run, cleared 180 F and stabilized around 190 F.

Ok, what could be causing this? I have the cold start on the MS set to 90 F as I had problems with correct sensing of
"warm running". I used the laptop to make sure when the temp was 160+ the engine was not in cold running mode.

So, would hotter plugs help? Why would the temperature have this effect?

Thoughts?

This is driving me nuts, as the car is doing well. The coil-over front suspension is working great!


-- brett

How are you triggering the mega squirt? Thermo fan for an oil cooler causing interference?
Fuel pickup not blocked or dry?
How high have you seen your Hp on a dyno?

Thanks for the reply.

I am using the tach signal from the second strike.
no thermo fan
fuel pressure stays constant.. Full tank of gas.
the dyno run was after the ms install. No previous data.

--brett

I'm just throwing ideas out nothing seems obvious
Using a tach signal for injection isn't always the most reliable and I would think that it would give you a more consistent problem if it was the cause. What sort of plugs and leads are you running. I'd always make sure they are spiral wires and resistor plugs
Are you getting smoke out the exhaust when it misses?
What sort of injector duty cycle do you reach?
Hopefully it sounds like an obvious problem and one of the other guys can chime in
Cheers
Edwin

Miss at that RPM could also point to Dist bearings wearing out.

Does the dist rotor wiggle at all?
It wouldn't be a condensor if you are using the "multispark second strike controller"
It has it's own cap discharge right?


Stu

Thanks Stu

I thought about the disty and did check shaft wobble. Even if that was it why did it go away at temp?

hum. Maybe a loose wire, znd not temp related... I might be chasing the wrong thing.

--brett

Everything is screaming ignition to me. Anyone else having issues with this second strike controller? It's hard to say if you have a timing issue, or this controller is intermittent with waste spark. Can the controller be set for single spark, if so, can you duplicate the problem in this mode?
You have a nice setup, but why not ditch the dizzy and have the megasquirt handle the ignition?
It would be nice to see more data. Return the car back to stock ignition and get a base line dyno run. Then reconnect your controller and set it up for single spark mode (if it's a possibility) and run it on the dyno again. Lastly, restore the ignition back to what you have it now, and do another run on the dyno. This would give you great data to work with, although pricey. 106hp seems low for what you have, but I'm not that familiar with the 2.7

Yep. The second strike has the ability to chznge the phase of the second spark. Setting to 0 will eliminate it.

I have ms 1, not 2. So, no ignition control. Though I am toying with the idea...

the 2.7 should make at least 150hp at the wheels.

--brett