Split: how they got > 200bhp + on a single plenum 16v

Who did you speak to Chris? Keith or Jim @ RPM? Or someone else now? Not been down their neck of the woods for years. Certainly used to build quick revving engines, mine was nuts - used to pop the charger bearing seal springs all the time from revving upto 8k extremely rapidly on my 1308cc G40 engine.

 

excellent, bet it's on alpha-N not map sensor

 

I think it is.

The thing is using the MAP sensor gives better load based fuelling as it accounts for changes in gradients and conditions that affect the load placed on the engine. However, as I think you already know, the downside is plenum pulses caused from high cammed motors upset MAP sensors and hence why the more crude alpha-N method is used.

Gurds

 

wonder what system they use on vtecs etc,

 

Yes Alpha N

My mates S60PRO is on Alpha N and Coolant temp sensor only (no Air Temp Sensor) Very Wild Cams

 

Honda VTEC (Plenum) = Speed density.

Additionally
Toyota 4 throttle 4AGE Intake only VCT 20v = MAF (siliver top) or MAP (black top)

 

I have been told in the past off alpha N setup with map sensor taking over only at certain set revs
The map sensor would also be their on start up to have some sort of barometer reading
Depending on where about you are. Some sort of hill climbing setup
I hope I made sense...

 

ABF plenum Group A clubman engine power plot:

• Black line: too rich mixture with good top end power: 209PS (206bhp) / 232NM (171 lb/ft)
• Lighter line: leaner mixture, better between 5,000- 6,250 rpm: 207PS (204 bhp) / 247NM (182 lb/ft)

Essentially Group A+ spec, on a plenum, but to a limited buget.

Additional relevant spec:

- larger ports than Group A & Kit Car 4-2-1 exhaust
- c/r above Group A (11.5:1) to about 12:1
- DTC GpN+ / GpA VW Digifant ECU mapping

 

Cannot understand how the leaner mixture only improved torque at 5400-6200rpm. That is unless there was another change or mapping was only concentrated at this breakpiont. If a leaner mixture was responsible for a torque increase I would have expected the 'hole' from ~3800rpm to 5000rpm to be filled. I could see there is more WOT performance to be had from that set up with further mapping development.

 

wondering what the definition of "lean" and "rich" is.... and if it was across the board adjustment, and not specific load/rpm points...

 

I woud also be interested in what 'top tuners' define as lean and rich at WOT at different parts of the rev range....

 

There is a potentiometer on the ecu, Lean< > Rich
After test 1 ,just adjusted towards Lean
No mapping or other changes were made before test 2

 

seems a bit... crude

 

This is on a Bosch ECU, or a wire going into it?

 

So by turning towards "lean" you are assuming that there was global shift in fuel mixture. The plot of before and after suggests optimisation occured around the new torque peak only with no change and even a loss in other points of the rev plot. Are you are liberty to say was mixture was seen on the lambda reader? I respect if you cannot.

 

so across the board adjustment then...
were afr's logged during these runs so the actual fueling is seen?

 

What would they define as Rich ? (AFR's)

and Lean ? (AFR's)

 

Any AFR (air fuel ratio) greater than stoichometry, which for E0 petrol engines is considered to be 14.7 parts of air to one part of fuel, is considered lean or in excess of air. Less than 14.7 and you have an air deficiency or rich running. The term lambda = 1 is derived from the above explanation, lambda can deviate as a % +/- 1. So 0.85 = 15% air deficiency = 12.5:1 AFR or AFR of 12.5


For maximum power/torque in a NASP 16v engine the LBT (lean best torque) AFRs ( generally), on petrol and for given MBT (max brake torque timing), can be from 13.0 to 12.0. Richer than this results in component cooling with some loss of torque. Richer than say 11.5 will significantly reduce torque. Experimentation, where many many WOT sweeps are made, determines what AFR the engine will achieve LBT per load/speed site. It takes a lot of time to get right when the all sites are optimised. More time when the engine is as custom built as in the plots shared by HPR.

 

Just 2 runs were done , and no intention to optimise output
No logs were made / there was no lambda sonde on the car
The dyno operator said during test 1 ``much to rich, ``and it was clear by watching the fumes it was
So we tried again after adjusting

The ecu was modified as used in grA with some soldering inside
Infact all that is needed is the homologated ecu housing and connector, electronics are free

Just dont know if the potentiometer adjust everything up /down or just some part of the range
( changing the shape of the curve , disgressive, linear, progressive)
I try to understand too , all i can say ,these were the results

 

Fair enough HPR.