Forum » General Tuning Discussion » Fuel Table numbers

Fuel Table numbers

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads

Page 1

Hi HPA family,

I am using LINK G4+, Tradition fuel Mode, K20 NA Engine.

I have noticed in my fuel table, when i am at High load ( 100 Kpa to 4000 -6500 RPM) the number in the fuel table is getting lower

Example - 100 KPA - 4000 PRM = 70 (in Fuel Table number)

100 KPA - 5000 PRM = 68.6 (in Fuel Table number)

100 KPA - 6500 PRM = 64 (in Fuel Table number)

Sometime Mid in the fuel table low load as well

someone can you explain how and why its happens ?


Attached Files

Pulsations in the intake and exhaust change with the engine speed, and thus will affect the engines volumetric efficiency (how much air mass it can take in relative to the engine displacement). Generally as the shape of the volumetric efficiency (or fuel map) will be similar to the torque curve of the engine.

Changing the cam timing will affect this. In your engine, the VTEC in high-position should help the high RPM maintain it's volumetric efficiency. If you were using VTEC in the low-position this will be more pronounced.

Can you confirm that you've got VTEC switched to high-position when you're at 5000 RPM and above?

To expand on that a little, as David said, the volumetric efficiency (cylinder filling) approximately follows the torque curve, so it is usual for the fuelling to drop off as the torque peak is passed.

The confusion some have is that because the engine will produce more power they think it will need more fuel - it does and it's done by having more opening events per minute, just smaller ones.

Also, as David said, with your engine there is VTEC to be considered, and how it's implimented, as often there is a 'double peak' when they aren't integrated properly (I would take a smooth transition over the 'kick') - you'll feel it as a surge in torque/power when it opens.

Thanks a lot for the reply David and Gord,

Currently, the VTEC switch is 3800 RPM and I gave some Conditions to VTEC should be work, Its work with dual fuel tables. when the VTEC is hit, table 2 will be activated.

I got your points, as Cam Pulsations are affects on the fuel table or VE.

I am confused here. As you said, the Fuel table curve is Smilier to the torque curve. so my fuel table curve is dropping at the higher RPM. what does that mean?

and the CAM angel is wrong that's why it is affected to the fuel table?


for your valuable time, knowledge and the experience to share with us

Attached Files

Torque, the turning 'force', is approximately in proportion same as the 'bang' in the cylinder turning the crankshaft, and the size of the 'bang' is approximately in proportion to the amount of air (and fuel) in the cylinder. So, from that, you can see that the fuel for the air is approximately in proportion to the torque. From that, you can see that more fuel, per engine revolution, should be needed around the torque peak and be less before, and after, when there is less air being drawn into the cylinder.

With the fuel for 'power', it depends on how much is needed for the air in the cylinder TIMES the number of times it is injected per minute - that is why the engine will use more total fuel, even if the individual injectors are supplying less fuel per cycle - eg peak torque may be x mS, but peak power only 0.8x mS, with the former being 50 times a second but the latter 100 times a second.

The camshaft(s) angle isn't 'wrong', but it has a big affect on how well the engine fills the cylinders at different rpm - the principle behind VTEC (and other variable camshafts) is to try and get the best cylinder filling (torque) at both lower rpm and upper rpm. If it is set up properly the camshafts should change over so the best cylinder filling happens at all rpm. You may be operating the VTEC so it swaps to the 'power' setting too early, costing performance - but you may not, depends on the specific setup you have.

Thanks a lot Gord.

I do understand, I got your points.

Thanks for your best support

While the torque will be less as the RPM rises, the Power may not be, since the equation for Power = RPM * Torque / 5252. So it's perfectly acceptable for your engine to produce less torque (but more will always make more power) as the engine speed rises, and still make the expected power.

Generally torque is only improved by processing more air, providing the optimum amount of fuel, and extracting the performance by getting the ignition timing correct.

Yes, devid do understand.

Thanks for your best support.