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VE table with a restrictor.

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Another FSAE question. I've been starting to attempt fixing the last teams VE table and noticed my log and lambda was value were making really low numbers. Like mid throttle 5k rpm VE numbers of 35. We do run a restrictor at 20mm that is machined like a Venturi. As just a broad strokes question should the restrictor really kill VE values. The KTM engine on the Dyno made similar peak values to what is published. I don't have the Dyno values as it was lost, but peak was 67whp. Just curious what things I should look out for with a restrictor. Happy to answer any questions.

KTM 690 single piston, giant throttle body, giant intake manifold, decent exhaust, Motec M150, happy to upload the tune for the curious

You can definitely expect the restrictor to affect the VE and what you're experiencing doesn't surprise me at all. I can't comment specifically on a VE of 35% and whether that is in the ball park but you do need to remember that the VE table is only going to be as accurate as the rest of the data. In other words you need to make sure that everything else is correct in the M150 setup first for the VE values to be correct. A good sanity check is that the VE table should approximate the shape of the engine's torque curve.

Thanks! As far as I can tell the data is in right. I fixed the injector data (flow, volts, pressure table stuff), prior team didn't have any data in other than flow. Finally got a fuel pressure sensor in and the pressure stabilized. MAP sensor is correct, finally. I'm not 100% on their values for the air temp but it does read a reasonable value. I am trying to get a GM AIT installed to solve that. I would have thought the restrictor would be a higher RPM/Power limiter and down low not much of an issue. I'll see where the data takes it.

Correct me if I am wrong, but from going through the webinars I want to check I get it. VE is the air flow of the motor. If VE is calibrated/done then I can just change the lambda target table to change the fuel ratios. Assuming nothing drastic changes like intake/exhaust/other than the VE can be left alone for the most part. Anything that changed pumping efficiency like intakes, or stuff, I'd have to re-evaluate the VE table. I have MegalogView HD for my car and made a histogram table for datalog tuning. I'm trying to use the i2 logs, Megalog, and the M1 VE table to do some trials with Lambda was. We'll see how it goes.

Attached the highlighted cells are where I started to stab at it. Doing it from logs is time consuming and was curious if the restrictor changed much. As soon as I can get a day where the team will let me get some good data I'll try some more.

Thanks for all the help and webinars

Attached Files

Thanks! As far as I can tell the data is in right. I fixed the injector data (flow, volts, pressure table stuff), prior team didn't have any data in other than flow. Finally got a fuel pressure sensor in and the pressure stabilized. MAP sensor is correct, finally. I'm not 100% on their values for the air temp but it does read a reasonable value. I am trying to get a GM AIT installed to solve that. I would have thought the restrictor would be a higher RPM/Power limiter and down low not much of an issue. I'll see where the data takes it.

Correct me if I am wrong, but from going through the webinars I want to check I get it. VE is the air flow of the motor. If VE is calibrated/done then I can just change the lambda target table to change the fuel ratios. Assuming nothing drastic changes like intake/exhaust/other than the VE can be left alone for the most part. Anything that changed pumping efficiency like intakes, or stuff, I'd have to re-evaluate the VE table. I have MegalogView HD for my car and made a histogram table for datalog tuning. I'm trying to use the i2 logs, Megalog, and the M1 VE table to do some trials with Lambda was. We'll see how it goes.

Attached the highlighted cells are where I started to stab at it. Doing it from logs is time consuming and was curious if the restrictor changed much. As soon as I can get a day where the team will let me get some good data I'll try some more.

Thanks for all the help and webinars

Attached Files

Thanks! As far as I can tell the data is in right. I fixed the injector data (flow, volts, pressure table stuff), prior team didn't have any data in other than flow. Finally got a fuel pressure sensor in and the pressure stabilized. MAP sensor is correct, finally. I'm not 100% on their values for the air temp but it does read a reasonable value. I am trying to get a GM AIT installed to solve that. I would have thought the restrictor would be a higher RPM/Power limiter and down low not much of an issue. I'll see where the data takes it.

Correct me if I am wrong, but from going through the webinars I want to check I get it. VE is the air flow of the motor. If VE is calibrated/done then I can just change the lambda target table to change the fuel ratios. Assuming nothing drastic changes like intake/exhaust/other than the VE can be left alone for the most part. Anything that changed pumping efficiency like intakes, or stuff, I'd have to re-evaluate the VE table. I have MegalogView HD for my car and made a histogram table for datalog tuning. I'm trying to use the i2 logs, Megalog, and the M1 VE table to do some trials with Lambda was. We'll see how it goes.

Attached the highlighted cells are where I started to stab at it. Doing it from logs is time consuming and was curious if the restrictor changed much. As soon as I can get a day where the team will let me get some good data I'll try some more.

Thanks for all the help and webinars

Attached Files

Are you running to the factory rev limit?

I would expect the ve table to look more like a regular torque curve at 100kPa, noting you may never be able to get that manifold pressure with the restrictor at higher revs. Looks to me like the ve table is compensating for fuel pressure fall off or the resonance of the intake/exhaust is heavily biased to redline which probably isn't great unless you are running a CVT.

I would argue that the restrictor should not effect the ve map so much as regular contributors like cam/head/manifolds, but limit the absolute pressure you can achieve in the top end (so VE at high rpm near atmosphere). I can believe a motor that is more cammy than most car engines having a very low VE at relatively low revs and pressure/throttle however i still think something is missing if you lambda is matching target table with that map shape.

I'm pretty sure some of your fuel injector settings are out unless the manifold/cam tune is genuinely rev limit biased.

Does torque delivery match the look of that?

It is the map 'tune', or 'map', that was handed to me from last year. It runs. Their lambda targets idled at 0.9 and go to .87 in a flat table chart. They went with rich is "safe". I'm trying to fix it. The VE table shown was not dialed for matching lambda targets. Rev limit is 9500 like the stock bike. Previously the fuel pressure was tanking from 50 down to 30ish at times as they had two fuel pressure regulators inline pre and post fuel rail. I've cranked the post rail one to the limit and put in a fuel pressure sensor. It seems stable now, but only have level 1 logging. As far as I can tell I've fixed the data inputs for injectors and the like. We have a massive intake manifold. I'll have to find out exactly, but if I recall its something like 8-10 liters in volume. It goes filter->throttle body -> restrictor -> manifold -> intake port

I'm trying to change as little as I can each time we take the car out as to limit the number of variables while I get it fixed. Most of my team just wants it to run as it has run for the last year. I've build another tune with lambda target tables that resemble something reasonable with idle about 1.0 and gets around 0.9 near heavy load. I plan to pull a few degrees of timing as I just got a knock sensor on the engine I need to get figured out. I currently don't have dyno access the car is a single seat and only level 1 logging, so I can't induce knock safely. We technically have a engine dyno, but it doesn't output values accurately and doesn't work currently. At some point I'd like a rolling dyno, but it destroys the soft tires on the car in very short time. There is no steady state hub dynos close either and we run a custom hub and mono nut so that's out. I'm trying to figure out the VE stuff because I know it is currently wrong, but not experienced enough to know what it should look like. I agree with it restricting power up top and I feel like the giant manifold does us no favors. Are there any examples of how the VE table looks like the torque curve? Not 100% I follow how that should look. Thanks for all the help.

If you have access to a hub dyno, you can build hub adapters for centerlock wheels. Here are some of the ones I've built for my Dynapack. The FSAE team that uses my dyno provides their own adapters (they have 3-bolt hubs!).

Attached Files

I've only seen datalogs from a few FSAE teams using VE fuel maps, but their numbers weren't too far off what I'd expect to see for unrestricted engines. On an FSAE car using a 4-cylinder sportbike engine and gasoline, MAP was around 97kPa at 3000 RPM and dropped to 82kPa at 13000 RPM. VE table values were in the 60's for the idle region of the map, and between 75-105 in the full throttle regions. It's not uncommon for different systems tend to need different VE numbers, so I wouldn't necessarily expect to see the same numbers for a Motec or Haltech or other standalone ECU with a VE map.

I've heard of an FSAE team who experienced problems due to mounting the fuel injector in a bad location in the intake manifold. Engine ran poorly and was down on power due to the fuel spray hitting the intake runner walls and not mixing well with the air on its way to the intake valve. The lambda trace was very rough even when the fuel pulse was smooth, and the RPM trace was also rough but that could be due to a Dynapack dyno having trouble keeping the ramp rate steady for such a small engine. They had brought their car to an experienced tuner / builder for dyno tuning, and I think he said they picked up 20+HP just from relocating the injector to a better location and/or angle in the intake runners.

If you can't access a dyno, can you or some of the engineering students calculate estimated power based on vehicle acceleration and gearing? Even if your numbers aren't absolutely accurate, a repeatable test can help see if your changes are improving acceleration. Again this is the sort of info that is probably covered in some of the road tuning courses here on HPAcademy.

Good luck and remember to pass your classes.