Ed's 1991 CQ: Progress!

[Mcstiff]

Looks like that is my issue.

[a_CQ]

I just caught up on last couple pages....I think you need to remove the turbo to fix it

Good luck...sorry can't be much help but sounds like you're close.

[TheArchitect]

Your not thinking of using a hall sensor for the TDC ref pin are you?

[Mcstiff]

Your not thinking of using a hall sensor for the TDC ref pin are you?

No; I am suggesting that the reason I was not seeing the crank trigger pin in VEMS is because my hall is bad (jumping the pins suggested this). I think I have a 3b distributor in the pile so I can avoid rebuilding one for now.

[Mcstiff]

Since I feel like I'm cruising on the failboat, does this look correct?

:dur: So, having the distributor in my hand, I notice that the alignment marks do not correspond with the window :bashtard: I still should have been seeing signal with the DMM/scope.

[Mcstiff]

Officially started it!

Hard to get a vid and juggle everything else. It starts but I still seem to have trigger issues and idle is not set so it fires over, hits like 1800 pops and dies

Progress anyway!

[HeartlessNomad12]

awesome feeling to know that there is life inside it, CONGRATS

[Mcstiff]

Thanks! It is great to have progress but somewhat bittersweet since my trigger noise seems to be causing problems.

[savagerocco]

The vems guys should just rework the crank sensor conditioning circuit. Both Elaw and my 4k are running stock crank sensors with out all the jimmying around with the tdc pin. I know this was originally done for the URS4 cars with the bigger trigger pin, but there have been enough people with this issue to justify reworking the circuit to work with the stock 7A and 3B pins.

[Marc]

The vems guys should just rework the crank sensor conditioning circuit. Both Elaw and my 4k are running stock crank sensors with out all the jimmying around with the tdc pin. I know this was originally done for the URS4 cars with the bigger trigger pin, but there have been enough people with this issue to justify reworking the circuit to work with the stock 7A and 3B pins.

we're not even 100% sure the issue is the ref pin at the moment. I'd like to see some oscilloscope traces first.

[Mcstiff]

Workin now so prob won't have more data till tomorrow.

[savagerocco]

I would have to say that the crank conditioning circuit needs tweaking so it will work with exisisting hardware. Obviously vems needs mods to work with the Audi tri tach so why not make it truly plug and play?

[Marc]

I would have to say that the crank conditioning circuit needs tweaking so it will work with exisisting hardware. Obviously vems needs mods to work with the Audi tri tach so why not make it truly plug and play?

if they were designing it to work only for the audi I'm sure it could be made better. things get more complicated when you try to support a range of hardware.

The vems in "auditrigger" configuration works quite well. These econoseal ecus are a lot more work to setup because when someone comes to me with problems I first need to figure out if its wired the way its supposed to be, amongst other things. The pnp ecus 99% of the time need no trigger alterations whatsoever. even some 7a flywheels get away with no mods.

[Mcstiff]

We'll get to sorted out

I was just reading about Helmholtz chambers, anyone use one?

Paraphrased from here.

Things you need to know to build the resonator:

-RPM that drone occurs at
-Number of cylinders (engines with simultaneous firing cylinders like the SRT-10 truck will divide this number by two)

You will also need to know the speed of sound. It varies with temperature, but is generally accepted to be 343m/s.

Say your I5 resonates at 3000rpms, right at cruising speed. You'll need to find the frequency of the drone. Units here are pulses per second, or Hertz.

f = RPM * pulses/rev * (1/60)

f = 3000 rev/min * 2.5 pulses/rev * (1/60)

f = 125 pulses/second = 125Hz

At 3000rpms, your I5 fires 2.5 times per revolution. RPM is in minutes, so divide by 60 to reduce to seconds. Now you need to find the length of the wave at the frequency you just calculated. Wavelength is denoted by lambda (»), units are meters.

» = v/f = speed of sound / frequency

» = (343m/s)/(125Hz)

» = 2.88 meters

This gives you the length of a full sound wave. The idea here is to reintroduce a sound wave into the exhaust that is 180° out of phase with your drone frequency. To do this, you build your resonator tube at exactly one-fourth the length of the resonant wave. By the time the sound wave enters the resonator tube, bounces off the end and re-enters the exhaust stream, the amplitude is exactly opposite of the drone frequency and will lower or eliminate the volume of the drone.

Dividing the wavelength by 4 gives you 0.72m, or about 2.36220472 feet.

[Marc]

We'll get to sorted out

definitely. if you are still having any troubles by the end of the month, I will be up at Pike's Peak and have access to a car if I need to come see you/the coupe to help finish up the triggering/tune. I can bring my o-scope and all that jaz, though I'm sure you can probably get access to one before then.

[Quattro v1.0]

Awe heck - If it's droning you're going too slow ;o]

[Mcstiff]

We'll get to sorted out

definitely. if you are still having any troubles by the end of the month, I will be up at Pike's Peak and have access to a car if I need to come see you/the coupe to help finish up the triggering/tune. I can bring my o-scope and all that jaz, though I'm sure you can probably get access to one before then.

At this point my goal is the be at the peak too but great to know!

quattro v1.0 wrote:[/quote]

Awe heck - If it's droning you're going too slow ;o][/quote]

I do live next to a school zone; the kids do like to go fast.

[Mcstiff]

Here is what I am seeing at the EC



I was having issues getting the back probe so I just pulled the pin. I may be able to log the scope if I can find the right memory card around the house. Is it worth trying to record the signal (back probed) with it "running"?

[Marc]

ah yes, it helps to go back a page and look some times. yep, switch polarity on the secondary trigger for the ref pin until that pulse looks the other way around (goes positive, then zero cross, then negative). your symptoms do line up with what I've seen for backwards polarity on the sec. trig. it will usually start but hits horrible trigger error around 2k.

[Mcstiff]

Cool, just swapped the pins. That old, purple, plastic is brittle as hell!!

[Mcstiff]

PROGRESS!!! Got ignition and a, high, idle!!! Phone died and lost the vid :banghead: but I have logs

[Marc]

PROGRESS!!! Got ignition and a, high, idle!!! Phone died and lost the vid :banghead: but I have logs

sweeeeeeeet. when you are ready, send me some datalogs and I will help you with the tuning side.

[Mcstiff]

I have a few things to assemble before I can nail down idle and have any useful driving logs.

[VWAudi4Life]

...
Dividing the wavelength by 4 gives you 0.343m, or about 1.12532808 feet (1/5=0.2744m or 0.900262467ft).

Interesting read! So which one is it? Divide by 4 or by 5?

[Mcstiff]

I think 5 since it seems based on the # of ignition events per rev but maybe I am missing something.