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VE table power Calculation with vtec

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hi folks !

This is Andrew and this is my today doubt ( I have many more ) :D

As I understand thanks to Andre, in a very easy and direct way, the more VE the more power ( same car-engine-setup ). I guess the higher the VE number the more efficiency we are achieving on the engine so more fuel and air is being burnt right? I will upload 2 photo-log so you see the difference between tune my car with the Vtec set at 4300 rpm and set at 5000 rpm. Those are from different day so probably there is a variation in Air specs.

As I Can see the 4300vtec Ve-logplot show me that I am doing more VE at same rpm as 5000vtec so I guess I am doing at least more torque? really? I dont really feel the car faster, I just hear the vtec kicking in sooner but my butdyno doesnt feel difference.

Then I should play around lowering the vtec to... 3000rpm for example and look if the VE keep on increasing on the mid range? Hondata manual doesnt recommend decreasing Vtec from 3500rpm I think, is this due to problems with oil pressure?

Many will think... wtf does this guy need more torque down there when he usually shift at 9000rpm (8660real rpm) and start pulling again at 6800rpm or so. Well I autoanswer myself, lets imagine this is only a MAXOUTOFITDYNOTUNE, so its porpouse is make max amount of torque and hp everywhere.

On the next chapter/question ignition transition when vtec kick in ;)

PD: I cant Find a log I did in high gear ( racetrack ) where I see the VE table decrease a bit after 8200rpm, this mean my peak power is there?

thx Andrew

Attached Files

I took a look at your .jpg files . What engine is this? The VE number needs to be tuned. It's an input, not an output.

Did you tune the VE table with the VTEC ON and the VTEC OFF and then change the switching points? or is the VE number different because changing the VTEC rpm moved you into a different area in the VE maps?

Understood, input.

Ve numbers are very accurate on the log as there is low egocor is that right?

Yes. I am running dual map on ve and ignition so at 5000rpm now goes from ve1 to ve3.

Yes. I Tuned the ve map this way. Vtec set at 3500 tune ve3 untill 7000 or so. Then set vtec at 7000 rpm and tune the ve1 until 8000 rpm or so. Is it ok right?

What more do you see? Is not my VE ok?

logs are on vtecmod zip on the first post.

As I told before, I have dual map for the vtec. Is a f20c engine s2000.

If you look at the VE even when the vtec is set at 5000rpm ( ve3 kick in ) there is a noticable VE increase at 6000rpm, is this probably because of the CAM? because the ignition goes up smoothly.

I have seen many ignition map were they ask directly 29º from 5000 to 9000 at full load, is this better or with smooth like mine? I guess that the correct fueling when no knock the car with 29º at 5000 rpm will do more power if the engine is able right?

The friend who help me to start on this allways told me that the maps should be smooth without spikes.

thx Andrew

Attached Files

Thank you for providing the additional information. I can't check your logs right now. I can't say whether your VE tables are good. They are probably "good enough" if EGO correction is low.

Remember though that the VE table is still just numbers. It is not an actual measurement in a lab. If you set the VE to 80% in the table, and the EGO correction is low, it doesn't mean that your actual VE is 80%.

I think it is best to test torque on a dyno. Think about it this way: your graph shows that 4300rpm is better, but factory VTEC switch point is 6000rpm I think.

"I have seen many ignition map were they ask directly 29º from 5000 to 9000 at full load, is this better or with smooth like mine?"

This is not a good way to do it. It is the old way to control ignition. On a very old distributor engine (mechanical ignition timing, no computers), that is how the ignition works. On electronic it can be smooth like yours. It's much better for high rpm power. Your way is better.

"If you look at the VE even when the vtec is set at 5000rpm ( ve3 kick in ) there is a noticable VE increase at 6000rpm, is this probably because of the CAM? because the ignition goes up smoothly."

6000rpm is the factory switching point so that doesn't surprise me.

"The friend who help me to start on this allways told me that the maps should be smooth without spikes."

Usually yes, but when you have variable cam or variable intake runner length things can get a little weird. The tuning of the intake and exhaust runners can cause certain rpms to have different behavior. So yes, try hard to make it smooth. But if you are sure you need to make a "not smooth" area, then do it.

It's best to tune VTEC engagement point and ignition timing based on measured power numbers using a dyno. The factory switch point was designed by engineers who needed to pass emissions and make the car feel the way the marketing department thinks the car should sound and feel. On most Honda engines you can find mid-range power gains by activating VTEC at a lower RPM than the original Honda ECU calibration. This will make the engine feel different, you won't feel as much of a 'kick' when VTEC kicks in at lower RPM. If you engage at too low of an RPM you will be losing power. It's tricky to estimate how much power the engine might make based on the VE table numbers and measured AFRs, checking power on the dyno is really the best way to go.

Arghx7

Indeed stock vtec point is 6000 but... I am selecting the vtec point at 5000rpm on the standalone and hear vtec kick in then... why do you think I have that VE change at 6000rpm?

I dont understand why 80% ve is not exact, I thought it were mathematics. Take your time to check the logs if posible ;)

AEM_SB

I have seen that the way to find the correct Vtec point is dyno a low vtec tune and a high vtec tune, then where both dyno power lines cross there, is the vtec, am right?

I was happy thinking VE was a good signal to know if the car was doing more power. I will have to finde a Dyno.

What can you tell me about the Ignvtectransition momento? when it goes from one map to the other you would smooth that point even more or keep like that? I have seen many do like 4-5º difference when vteck kick in.

thank you for your inputs.

My next stage was starting playing with the intakes, different size but If the VE doesnt help me to know if I do more or less power then is useless, my idea was to check if more VE was asked when replacing different intake size.

Regarding the transition, yes you will usually find that the torque curves for the 'big cam' and 'small cam' position will overlap at a certain RPM. When you set the VTEC transition point to that RPM, you should see the best torque curve. You might need to move it around by 100-200 RPM from that overlap point to get the very best results, but this should get you very close. You will probably find that both maps will overlap in terms of ignition timing and VE numbers at that same RPM where the torque curves overlap.

The VETable numbers might be useful for estimating engine power, but sometimes a car will need weird numbers in the VETable to compensate for differences in fuel pressure or even intake manifold & exhaust manifold harmonics that prevent the engine from using air and/or fuel efficiently. Using a dyno is one of the best ways to measure if the engine is making better power.

One of your earlier posts described adding ignition and looking for knock. For ignition timing, there is often a range of values that are 'close enough' to make good power without knocking. Using the highest ignition timing that doesn't knock is less safe than using the lowest value that will still make good power and leave a good safety margin for avoiding knock. Andre here at HP Academy has done some great videos describing this concept, some people use the term 'minimum ignition timing for best torque' to describe it.

totally understood, thanks for your inputs. Indeed as I watched at Andre videotutorial I dont have to find the ignition value just before the knock because probably at that value torque can be even decreasing.

I guess that VE can help telling me if a different intake or exhaust is doing better job than oem or not, am I right?

I have to say that the car was at first tuned with HFC and later with a decat, with a decat when vtec kicked in and at higher rpm I needed more ve/fuel value as it started to tend to what I think that is lean 1.1 lambda.

thx