16v Cars

[Eric Parham]

Thanks Jim. I went back and looked for their names in the results for the July 23 race at the Glen, and it looks like John turned a 2:23.9 on the long course (not too shabby ), but was down 2 laps for some reason. Do you know if his is a 2.0 or a 1.8 car? George DNS. Please PM me if you have contact info handy for either.

[shwah]

CIS systems also do a much better job of atomizing fuel than 'electronic' fuel injection systems.

CIS-E Motronic has a larger fuel plunger and can support a higher max hp than CIS-E; neither of which really matters for IT spec engines.

The mass air flow sensor in CIS type systems sure may seem like a big restriction when you look at it, but if you consider the size of the opening, and the cross sectional area exposed when you raise the flow plate, I don't think it is as restrictive as people expect.

[Eric Parham]

CIS systems also do a much better job of atomizing fuel than 'electronic' fuel injection systems.[/b]

That used to be very true, and may still be true to some extent, but many modern EFI injectors now have excellent atomization.

CIS-E Motronic has a larger fuel plunger and can support a higher max hp than CIS-E; neither of which really matters for IT spec engines.[/b]

Yes, a slightly longer rod with slightly longer fuel metering slits, as I recall, but no additional functions. They're the same animal for our purposes.

The mass air flow sensor in CIS type systems sure may seem like a big restriction when you look at it, but if you consider the size of the opening, and the cross sectional area exposed when you raise the flow plate, I don't think it is as restrictive as people expect.[/b]

Depends a lot on the control pressure for CIS-basic and CIS-lambda (that's another reason why we try to reduce it). I believe that CIS-E and CIS-Motronic may not be tunable in the same way, but I haven't reviewed it lately. If I'm correct, they may be even worse for our purposes than the older stuff.

[shwah]

It is painfully easy to tune CIS-E.

Get yourself a 0-10k linear potentiometer. Install it in line with the coolant temperature sensor. Go to a dyno and make some runs while measuring air/fuel ratio with a wideband O2 sensor. Turn the potentiometer until you find the optimum setting for power (typically 12.7:1 on these motors). Measure the resulting resistance, and replace the potentiometer with a fixed resistor of that value. People use different methods of switching this enrichment device into and out of the circuit manually or automatically based on WOT switch.

It is consistent, reliable and functional. One thing you are giving up to a programmable system is ignition mapping ability, but in the racing operation range you are typically at max timing regardless of the lower load/speed maps, making this a moot point.

[Eric Parham]

It is painfully easy to tune CIS-E.

Get yourself a 0-10k linear potentiometer. Install it in line with the coolant temperature sensor. Go to a dyno and make some runs while measuring air/fuel ratio with a wideband O2 sensor. Turn the potentiometer until you find the optimum setting for power (typically 12.7:1 on these motors). Measure the resulting resistance, and replace the potentiometer with a fixed resistor of that value. People use different methods of switching this enrichment device into and out of the circuit manually or automatically based on WOT switch.

It is consistent, reliable and functional. One thing you are giving up to a programmable system is ignition mapping ability, but in the racing operation range you are typically at max timing regardless of the lower load/speed maps, making this a moot point.
[/b]

I do agree that the limited adjustments that are possible with CIS-E are easy, but as with most things in life, I'm afraid that the gains are proportional to the difficulty (i.e., not much gain for the easy work). I actually had to do as you suggest with an added potentiometer on a street car once. I put a 16V engine into an 8V GTI and had to make do with the 8V fuel computer. Fortunately, I was able to use a digital multimeter to measure the milliamp current at the fuel pressure actuator and did not have to pay for any dyno time to adjust the pot.

The point I was trying to make in my last post is: 1) the control pressure can be reduced for CIS-basic and CIS-Lambda, and the reduction in control pressure reduces the downward force on the fuel-metering plate thereby reducing intake restriction, in addition to increasing injector pressure; but 2) the force on the fuel metering plate cannot be reduced in this manner for CIS-E and CIS-E-Motronic (collectively "CIS-E"). Also, any reduction to the force on these CIS-E systems would cause a reduction in injector pressure (the opposite of the older systems). Thus, while tuning the basic offset for the fuel mixture may be easy, these CIS-E systems simply cannot be tuned to reduce intake restriction like the older ones could.

[shwah]

OK. I see your point. I honestly just don't have enough CIS 'basic' experience to know that you tune the control pressure for fueling, which in turn reduces the resistance provided by the airflow plate.

FWIW that simple CIS-E tuning method can offer 20+ hp in situations. The factory system runs lean, especially at higher rpm.

[shwah]

I must have been asleep at the keys last night.

I should have mentioned that the CIS-E system also reduces the control pressure to affect mixture, which reduces the tension on the airflow plate. It just uses a different mechanism to do so - this is the DPR that you measured the miliamps at when tuning your street car.

[Eric Parham]

I must have been asleep at the keys last night.

I should have mentioned that the CIS-E system also reduces the control pressure to affect mixture, which reduces the tension on the airflow plate. It just uses a different mechanism to do so - this is the DPR that you measured the miliamps at when tuning your street car.
[/b]

I believe that is incorrect. I seem to remember that the plunger and plate are controlled by SYSTEM pressure in CIS-E, and not by control pressure as in the slightly older CIS. Yup, verified. See ch. 5, p. 24, Fig. 5-10 of Bosch Fuel Injection and Engine Management, Probst 1989 (Robert Bentley Pub). The so-called "pressure actuator" in CIS-E only controls the fuel flow to the injectors, and this controlled flow cannot affect the force on the plunger or plate. It might be a slightly more accurate way of regulating injector pressure, but it sure takes away one of the greatest tuning features of the older CIS.

[shwah]

The differential pressure regulator is what varies the fueling in CIS-E. As the name implies it varies the differential pressure across the system, it does so by changing the control pressure.

[pfcs49]

Sorry Swah, but he's right. I even consulted my Probst to be certain. phil

[shwah]

OK. Chalk up one more in the wrong column for me.

[Eric Parham]

FWIW, I wish you'd been right.

[shwah]

I think I am going to rig up a flow bench type test with my shop-vac and compare the Digi and CIS-E air metering systems at different positions of the metering 'doors'. Maybe later in the winter I will get around to this.

[Bildon]

>> I think I am going to rig up a flow bench type test with my shop-vac

As accurate as any Superflow. And that's not my opinion. It was proven at a Ford engineering facility.

http://www.flowperformance.com

[shwah]

Thanks for the link Bill.

[shwah]

Didn't catch that until it was quoted above. $25k?!

Some of these $$ numbers people assume are required to build a car still floor me. Sure if you pay for all the work, it takes a big checkbook, and for many that is the only way they have time to race. I totally respect that. However, what I see at the race track is that most IT racers are of the more budget minded type, who are more than willing to figure out how to do much of this stuff themeselves, or do things a different way - think for themselves and try the 'wrong' way that does not invovle buying the 'trick' parts offered by race shops - and succeed.

I don't believe for a second that $25k is any kind of threshold or standard to define a 'fully built' ITA car. Especially with the A2 Golf, the existing chassis development is extensive, the parts are available, they are not outrageously expensive, and they are tested in almost every ITB race across the country every year. The only missing peice is the motor for the 16v, and if you are putting $10k into that motor, you are spending too much IMO.

[Greg Amy]

Chris, I got the same response a year or so ago when I stated it would take $15k minimum to build a pointy-end Spec Miata; nowadays the entry price for a winning SM is double that.

I can respect your opinion, but I place you firmly in the "Dave Gran Camp" of "what it takes to race", not "what it takes to win everything". There's nothing - absolutely nothing - wrong with that attitude, either.

But, there's just NO WAY you can build a nationally-competitive ARRC-winning ITA car for much less than that. Even if you bought one ready to go, there's going to be a lot of work to do. The ONLY way you can do it is if you possess ALL the skills for building a race car and can do it yourself: welding, fabrication, engine builds, transmission builds, chassis development, have the equipment to bust and balance your own tires, you own an engine dyno, you own a shock dyno, etc. And that's only if you put ZERO value on your time; well, if you have all this equipment and skills then you're a genius and you simply can't do that!

Are you like that? Not me! Know anyone like that that's willing to build it for you for free? Please send me their contact info...!

On the way home from Atlanta we bantered about what it would take to replicate the NX2000, given what we know now. We figured out that it would take approximately $13-15,000 just in car, rebuldable engines and trans, performance and replacement parts, supplies, and sublet work (machine work, final welding, etc). And that's with zero value on anyone's time. And that's with everything already figured out. It doesn't take a math wiz to figure out that we've "invested" (hah!) a hell of a lot more than that.

Smart? Hardly. Worth it? Well, this week it is...don't know about next week, though

[shwah]

See I know what you are doing here.

Just when I feel like I have my B car ready to be competitive, and have started to think about a future FProd effort, you are trying to draw me into ITA by saying it can't be done :P . I love a challenge, and it would be tempting to make a move that lets me re-use so many components and spares.

FWIW - I am not in any way satisfied with just being out there. I just keep reminding myself that running the past few years with a used stock motor was making me a better driver, allowing me to focus on chassis setup, and keep hoping that I made myself good enough in the process to justify the motor build taking place this winter. It takes time to get there, and I hope I am getting closer, but IMO you race to win or don't bother. If the new family dynamic allows (new baby due March, #2!) I hope to be measuring how much farther I have to go at Road Atlanta next fall.

I don't doubt that your effort was a costly one, but there is a huge difference between making an 'oddball' competitve and making a known quantity competitive. I have an honest $5-6k in my car. It is under weight, has exactly the gearbox I want, has exactly the cage I want, has the suspension I want and is waiting on the engine I need as well as the 'right' tires. Development never stops but I expect to have an all out ITB car under me by the end of next season for less than $10k. I don't see how running the same car with a differnt engine (needs to be a different shell due to VIN but the are the same thing) adds $15k to the mix.

Of course I may also post back here next winter to report that we have an honest $15k into the mix to be competitve. Time will tell.

[Greg Amy]

I honestly, truly, sincerely wish the best in that effort. In fact, prove it can be done and I may be back in the VWoA camp!

But this racing stuff is pure EVIL! Man, if I could be a future-Stan and travel back 5 years, and say, "Dude! You're gonna win the ARRC one year! Great job!! And *this* is what you're gonna spend in money, time, effort, and mental abuse to get there!" I'd go back and slap myself more-stupid or something like that...

Evil. Pure evil.

[shwah]

Agreed, pure evil

Didn't mean to imply that I would go win the ARRC. But that IS the goal in doing this IMO. If you don't set the target, you are unlikely to hit it. I expect to have a very capable car, and go down to have some hard lessons taught to me next year. No other way to find out where I stand.