Manifold Runner I.D. Parameters

Hello there. I'm a newby looking for help to a rather unusual problem.

I have stuffed a 2.3 Ranger Duratec into a Sunbeam Alpine. It pulls very well at low rpm, but runs out of steam by 5,000, then recovers a little. It has an aftermarket EMC, here is the fuel map profile that has been generated for max hp at WOT. I am offering it as I think it represents the VE profile and hp generation.

RPM Fuel value

1.0k - 1.03

1.5k - 1.06

2.0k - 1.10

2.5k - 1.11

3.0k - 1.13

3.5k - 1.15

4.0k - 1.14

4.5k - 1.11

5.0k - 1.04

5.5k - .96

6.0k - 1.04

6.5k - 1.07

Note the severe dip at 5.5k and subsequent recovery.

A note of description. Internally, the engine is a dead stock 2002 Ranger. The exhaust header is a homemade "shorty", 4 into 1 flat collector with 1.5" I.D. runners. The primaries are in the 14-16" range, exhaust system is 2", welded up from mandrel bent shapes. The intake has 1.5" I.D. runners, 22" long from intake valve to plenum. The plenum has about 50% of engine displacement.

The only thing that see that is unusual is the length of the intake runners. I'm thinking there is a resonance that is causing the problem. Taking another look at the engine, I think I can reduce the runner length to anything from 14" - 16".

Any ideas how this will impact the dip? Also, thoughts on intake runner I.D.?

Bill

I mentioned this in another intake thread...

Ive seen where development teams will make a "test Manifold" of sorts where the runners are made by using a length of pipe that fits snugly into another length. By changing the amount of pipe overlap, you get different runner length. Jig it up so it remains stationary between pulls, and you can adjust the length-tune for max performance wherever you need to make power in the RPM range for your application. Take measurements when you find the best length and voila...

In reply to 4cylndrfury:

That's really not much of a choice for me. Space constraints are such that I have a choice, either 22" or something in the 14"-16" range. I cannot do 21" or 17".

Bill