The V8 Owners Forum -

I have a modified EFi manifold with bigger shortened trumpets. On wheel dyno the torque curve has a dip at around 3500 rpm. Have you seen typical behaviour with modified intakes that some of you might run ?

Below is the dyno curve. I cropped the numbers since they are irrelevant. Also spark problem limited the run to roughly 4700 rpm.

Pics of the intake in here: http://www.v8forum.co.uk/forum/viewtopic.php?t=14223

In my mind your problem is with engine magnament system, not trumbet base..
Maybe VR-sensor desync problem or lean/rich spike on fuel map??

You will get resonances in the intake between the valve and the top of the trumpet.
At some engine speeds they help, some they hinder. The manufacturers geometry was designed and tuned to a certain characteristic.

The exhaust will have a similar effect.

I wonder if experimentally just changing the trumpet base and nothing else would be instructive.

Chris.

The fuel curve was very steady throughout the pull. Intake / exhaust combination vs. resonance is what the dyno guy suspected too. Therefore the reason for the enquiry.

At resonance, I'd expect a peak rather than dip? As the airflow should speed up?

DaveEFI wrote:At resonance, I'd expect a peak rather than dip? As the airflow should speed up?

I am pretty sure you can get either.

Chris.

Can you feel the dip in torque when driving?

Tom.

Not in 1st or 2nd gear. It now hits the limiter hard at 6000+ so that issue is sorted. And in highr gears I am close to loosing the lisence due to excessive speeding anyway. Basically it is just an annoying issue. Besides, we never got around to sorting the complete fuel side let alone the ignition charts so maybe there is some fine tuning to do. At the moment work and mandatory summer holiday with the boss in the family hinders any further setup.

It's a pretty huge dip...any datalogs of when it happens ?

ie to check fueling, timing and whether injector PW's actually reflect any changes you might be seeing with either

Yes we did log one pull but for some reason the Haltech software will not open its own log files

I will continue with setting up once the family commitments are taken care of. I will opdate once there is something to tell...

minorv8 wrote:Yes we did log one pull but for some reason the Haltech software will not open its own log files

I will continue with setting up once the family commitments are taken care of. I will opdate once there is something to tell...

Dunno if it is right one, but there is a data log viewer available here:-

http://www.haltech.com/downloads-2/ecu- ... -firmware/

It's not unusual to have separate software for tuning and log viewing - to keep the progs down in size for phones or whatever.

I doubt that this software is compatible with older ECU versions like mine... I will have to try it anyway as well as try to get some other logs to see if I always get the same error message.

Log function is nice when it works

minorv8 wrote:I doubt that this software is compatible with older ECU versions like mine... I will have to try it anyway as well as try to get some other logs to see if I always get the same error message.

Log function is nice when it works

If it has a logging function, there surely must be a way of viewing it?
What type of file does it save as?

There is also a viewing function but when opening the log file it throws an error.

e.g. "0.000000 is not a valid floating point"

The file type is a Haltech .csv

If it's .csv it should just be a generic log file ( indeed a generic file, excel viewable etc )

What age/model of ecu is it ?

Can you upload or email the log file ?