VE Table is squashed between 80 and 100 KPa

ptownsin · Post by **ptownsin** » Wed May 03, 2006 1:51 am

I've just got my car running with a rough set-up using MS&S Extra 024 code.
It's a 2ltr Ford Pinto (from a UK Sierra) thats had quite a lot of head flow work, big valves and, I was told, a cam for rallying.
Ignition is the Ford TFI code and distributor.
GSXR 750 throttle bodies supply fuel.

I'm quite happy with the full throttle VE bins and the car feels faster than it did when it was running webers.

Idle MAP is about 60KPa at best after tuning the throttle stop and the idle VE and at cruise it's about 80KPa. On overrun I've seen MAP as low as 25KPa.
I tuned the full throttle bins by hand watching a wideband output (12:1 AFR) and used autotune to do the cruise, but I have a dip in the table at the cruise point.

My question is, am I loosing out by having such a steep VE table from 80-100 KPA and having such a flat table lower than 80KPa?

Attached is the MSQ.

Cheers

Paul.

Cairb · Post by **Cairb** » Wed May 03, 2006 3:50 am

I found a similar characteristic on a 2.3 Duratec on ITB's, the VE table almost doubled from 90-100kpa. I switch to a hybrid form of alpha-n which has improved the feel of the car. On my setup I commoned the tappings from each body through a restrictor into a reservoir to get a damped but responsive MAP signal. I felt that any MAP variation due to pulsing would have a large effect on the fire to fire AFR although the average AFR may look ok.

I currently use the MAP signal as a VE multiplier to give some level of load sensing although thats not quite correct from analysis it's ok to drive.

I use MAP based AFR table and MAP based ignition map.

Cheers,

Colin

ptownsin · Post by **ptownsin** » Thu May 04, 2006 2:31 am

Thanks Colin,
I think I'll have to spend the weekend re-tuning the way you say.

I'd still be interrested to know what causes it as I've seen a toyota table thats not far from the suggested bins you get from the table generator, and this one had been on a rolling road. There were hardly and bumps in the table.
Is it all down to the cams I have or are there other factors like TB size (mine are probably too big at 42mm) or could I have an air leak?

Cheers

Paul.

Karl_Skewes · Post by **Karl_Skewes** » Thu May 04, 2006 2:49 pm

I've found that it's best to concentrate the bins in that 80->100kpa region.. especially 90-100kpa...
The ones below that can be spaced out a lot.

Check out the VE tables on our ITB setups on http://www.garagedori.com/tech

Great thing about adjustable rows is you can adjust them

ptownsin · Post by **ptownsin** » Fri May 05, 2006 7:43 am

Thanks for that link too Karl.

One of those VEX files looks similar where the VE rises over 80KPa and I'm guessing thats still drivable?

Paul.

Karl_Skewes · Post by **Karl_Skewes** » Fri May 05, 2006 7:25 pm

the redtop 4age with ITB one had a little bit of time on it with the wideband.
Those VE tables are actually accurately describing how much fuel is required relatively to MAP and RPM.... so not just driveable, that's how they are!