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Dean, it's me, Melvin, we've spoken before. We have to hook up one day. Unfortunately my car is down again (couldn't stand looking at the RPS kit :eek: ). I'm doing the fuel and I also dumped the RPS partial kit. I hope to have it up and running by the end of next week.....

As far as the guy tuning his car I asked and I think he said he's using the Apexi S/AFC (sorry, getting old). I do know he said the tech article is on the MKIV site (just looked and I couldn't find it).

I'm going to be seeing him again this weekend and I'm either going to record our conversation (if he'll agree to it) about his setup or take notes, seriously. Then I'm going to try to answer some of the questions posted here. I hate when a thread is started and then left open and everyone is just left hangin. So I promise I'll do my best to get you guys the info you want about his setup, that's unless he objects, which he already told me he didn't mind, he just didn't want to be flooded with emails and questions from everyone.

Melvin
 

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KansaiSupra said:
Thanks for the reply about the MAP. So how does the MAP work, The Jspec car still have maf's right? For the MAP what are the differences in the ECU....


Thanks
leonard
Thare are 2 types of fuel metering in common use: Speed/Density and Mass Air.

Speed Density systems use a number of sensors to infer, not directly measure, the amount of air. Typically they have a MAP (Manifold Absolute Pressure), Barometric pressure, throttle position and intake air temp as their major inputs. All of these input to the ECU which uses them to aproximate the amount of air, and thus the amount of fuel that needs to be added.

Mass Air systems share many of the same sensors, but the major difference is they use some method (Hot wire is the most common) to directly measure the *mass* of the incoming air.

Speed density systems have less intake restriction but cannot adapt as well to large changes to airflow due to modification w/o programming the ECU. They also do not control the A/F ratio as well since they are less accurate than mass airflow sensors at measuring the amount of ingested air.

The VPC converts the supras mass air system to a speed/density one.
 

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Lagtime said:


Speed density systems have less intake restriction but cannot adapt as well to large changes to airflow due to modification w/o programming the ECU. They also do not control the A/F ratio as well since they are less accurate than mass airflow sensors at measuring the amount of ingested air.

Chip:

On the Supra, do large changes to airflow cause problems and do problems with controlling the A/F occur when using a VPC?

I understand what you wrote is theory, but are there really problems with the Supra when using the VPC speed/density system?

If so, how long does it take the car to recover and run accurately? Is this a momentary issue or would it last for more than a couple seconds?

Just curious if it would affect 1/4 mile passes as the airflow is increased with boost?

Thanks!

Mello2:

Looking forward to getting some feedback on the dual MAFs!!! Is your friend tuning the fuel on a dyno? It would be great to see the A/F.
 
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Maury, yep dyno tuned. They just finished up a T04R install last weekend (on someone elses car) and doing the fuel this weekend and then dyno and tune. I think he said he was going to bring his car out again too. I'm hoping to have my car ready by that time too, the data/comparisons should be interesting and the get together will be fun.

Everyone interested will know the results.

Melvin
 

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Spool said:



Chip:

On the Supra, do large changes to airflow cause problems and do problems with controlling the A/F occur when using a VPC?

I understand what you wrote is theory, but are there really problems with the Supra when using the VPC speed/density system?

If so, how long does it take the car to recover and run accurately? Is this a momentary issue or would it last for more than a couple seconds?

Just curious if it would affect 1/4 mile passes as the airflow is increased with boost?

Thanks!

Maury,

The VPC has a chip that is burned with information appropriate to the injector size you are using, I believe that takes care of the basic tuning issues, the rest are resolved by using a GCC/AFC.

I would love to have access to a larger MAF sensor in the same way that ProM and others make them for the mustangs, for example. We are just too small a market it seems.
 

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Looks like you could remove quite a bit of material from the stock MAF. Not sure if it would disrupt airflow too much though...the four braces and middle plastic are shaped for better airflow.

I didn't realize just how much area in the intake path that the MAF takes up...it's quite a bit.

Also, I noticed a BIG difference in boost levels after installing the VPC. I had to turn the DSBC controller down from 54 Ratio to 48 Ratio to stay at the same boost levels in 3rd gear...1.22 kg/cm2.
 
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Is there any known way to port or modify the stock MAF to improve flow?

Thanks,

Adam
 

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Here is a photo of a MAF bypass done on a single turbo car:
http://www.mkiv.com/tmp/maf_bypass.jpg

Theoretically, there is no reason this shouldn't work as well as a dual MAF or VPC if the extra pathways are large enough to remove the restriction. The increase in airflow through each branch of the system _should_ be linear. At least that is what I'm told. People have been doing this for a while with DSMs.

The problem is routing the piping for the BOV and idle air control back to the intake. This shouldn't be too hard if flexible rubber piping is used, but you would still have to have some way of attaching it to the intake pipe before the turbo. I guess it all depends if your willing to spend $1000 or work a few more hours.

Chip: Why wouldn't another MAF work? Hot-wire MAFs should have 2 outputs to the ECU, airflow voltage and intake temp. Match any MAF up to the right injectors, tune the AFC a little and it should work. Only problem I see is that if mustang guys use 2 MAFs, one for each bank, you might not be able to find one that flows enough.

I would not do this without some datalogging software to read fuel trim (which I have :)). You should be able to ajust the size of the intake leak until it is matched up to your injectors by reading the long term fuel trim of the car. If anyone can suggest a good ajustable valve to use, I'll try it on my BPU car. You could do it w/o looking at this info, but remember if the trim goes over +/- 10% it effects WOT fuel trim as well, which could present a problem if the ECU was reset. If the car was tuned with a +6% correction to WOT, reseting the ECU and flooring it would make it go lean.
 

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Grant

That pic is killer...where did you get that?

Now that's innovation, you definitely could build a circuit for that...right? Sounds like it!

How is this car running?
 

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Mohd posted the pic a while ago. This topic has been discused in depth on the list.

If you have a AFC, you shouldn't need a circuit, since it allows broad ajustment of fuel trim (at least I think it does, I don't have one). Just add a bypass pipe, and ajust the fuel trim on the AFC until the ECU stops giving much of a lean correction. Should be very easy to tune. When I get my FJO wideband O2 I'll try it.

Unfortunately, my SFC only allows tuning on a per-rpm bases, which means the idle will be slightly off (first ajustment point is 1000rpm). Don't know if this will effect anything.

I don't know how this car is running, I think they mentioned it ran as good as a VPC car. I don't see why they shouldn't. Bryce made ~620rwhp with this setup. Only thing is that if you run more than ~400rwhp worth of air through the MAF it will be a restrction.

I'm sure the stock market won't recover any time soon, so I have about $0 for mods.... Sigh....
 
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