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I don't have that problem. Probably has to do with how good your part throttle mapping is.

Hesitation with MAP blipping the throttle may have to do with the delay between you hit the throttle and the time it takes for the MAP sensor to register the change in pressure. I know that GoTech has a newer chip where you can set up compensation for this. Switching to TPS should solve this, but may require retuning of the map I would think - not sure there is a generic relation between the TPS signal of an arbitrary TPS sensor and the MAP signal of the GoTech MAP sensor.

On my standard GoTech verde I had no hesitation at part throttle, but a slight hesitation blipping the throttle while free reving. In practice you wouldn't notice. On the pro GoTech 3.7 there was no hesitation anywhere.

It is tedious and takes time to tune driveability to prefection! Unless you are a pro, of course.

Jes

Zamani wrote:I don't have that problem. Probably has to do with how good your part throttle mapping is.

ar4me wrote:Hesitation with MAP blipping the throttle may have to do with the delay between you hit the throttle and the time it takes for the MAP sensor to register the change in pressure. I know that GoTech has a newer chip where you can set up compensation for this. Switching to TPS should solve this, but may require retuning of the map I would think - not sure there is a generic relation between the TPS signal of an arbitrary TPS sensor and the MAP signal of the GoTech MAP sensor.

On my standard GoTech verde I had no hesitation at part throttle, but a slight hesitation blipping the throttle while free reving. In practice you wouldn't notice. On the pro GoTech 3.7 there was no hesitation anywhere.

It is tedious and takes time to tune driveability to prefection! Unless you are a pro, of course.

Jes

Maybe you're talking about two different things. Throttle response from a completely shut butterfly will always be quite bad because it will take time to fill the plenum with air. You can clearly hear this if you have an "open" filter onthe car, just stomp the gas pedal and hear that sucking noise when the plenum is filled and when the engine hesitates.

If you have hesitation from pert throttle you should look into accel enrichment and ignition timing.

I had the car dyno'd and recorded again - this time with a straight through pipe replacing the rear exhaust section.
The sound recordings are for a yet-to-be-released video game. Details to follow when the game ships...



PS: Seems to work best when you right click link and first save file to your local machine, then play it.

Any improvements in the power department?

Yes, max power went up 7.1 Hp (to 183.1) max torque up 9.8 ft-lbs (to 174.1).
I should also say that the car had a pretty crude straight pipe installed - they used a crimper, no mandrel bends. It was welded up for temporary use, just to get the sound recording. With a proper pipe, you would doubtless see an even bigger improvement!

Anyone experimented with the best pipe diameter for a 24v 3.0 liter? Its obvious that I'm going to need some pretty radical exhaust improvements when I install the 24v.

Beninca told me 2.25" downpipes per bank and then 2.5" all the way.

I'm not sure what is best but I'm going with 1.875" primaries and a twin 2.5" system from there back for my 24v.

Mike,

Was the peak achieved at a higher RPM? I have a 2" S tail end coming out from a 2.25" muffler. The problem is my peak power is only at 5700 rpm the last time I dynoed it. I think a bigger exhaust may net me more bhp.

The dyno shop only tested to 6000 rpms and that is where the measured peak was. HP output increase had started to trail off above 5500 rpms, but the trend was still nicely upwards even at 6k. I imagine it would have made 188(?) at 6500 rpms, which is generally my shift-point at the track. The peak measures was 183 so I think another 5 HP seems feasible. This seems pretty good to me for an engine of this vintage given that its RWHP - you gotta love Alfa engines. They were running race gas, but that was only to avoid pinging and the timing was not advanced for the testing.

I've always been dubious as to the accuracy of the stock rev counter so have been conservative as reagrds shifting. I'll likely install an aftermarket rev counter when the 24v goes in.... and I think the GoTech allows the use of a shift light too

Cheers,

Here is the graph - the baseline was the one done a few months ago with the stock rear pipe - new test is the darker blue line.