The infamous 5k Flatspot!!

[Dubcharged 0]

This one has been doing our heads in at SNS, Pitstop and G-Werks. But we seem to be coming to the light at the end of the tunnel.

 

Consider this: 2 G60 corrado's. Similar age, same mods. We put a stage 5 No Lag in car 1 and it goes mental - as expected, nice smooth power line good fuelling and No Lag.

 

We put the same chip in car2 and it seems to be just as good until the car hits around 4800-5200rpm at which point the acceleration seems to die off then comes back in. a FLAT!

 

WHY?? Same cars, same mods, no leaks etc, SAME CHIP!! AAAAAGGGHH

 

Yes, we were losing it, hair has become thinner and bald patches have emerged!

 

We all know that if there is something critical which is slightly faulty, you wont notice it at 160bhp and you probably wont see it so much more with a mild chip. But the fault will be aggravated and rear its head with an aggressive chip which is what we're all about since we can be more aggressive due to our No Lag © coding.

 

So what could be causing this? After some head scratching, Pitstop identified the dizzy - in particular the hall sendor. Replacing this cleared the flat on cars they had in the garage with an SNS chip etc etc.

 

To illustrate this, Steve himself started experiencing a flatspot in his G40 - a new dizzy cured the problem.

 

So how could a hall sendor cause this?

 

The hall sendor is a magnetic device and its getting old. In a lot of cases 10-13 years so its gonna be wearing out. If the shaft develops horizontal/vertical play then you will get phase/jitter which will cause a misread in the ecu. The ecu counts rpm twice, once per hall and once per revolution so if it sees a dodgy signal from the hall at some point it would have to go into safe mode. Safe mode would be the last line of the map ie. max injector which is safer than no injector. VW probably anticipated such a fault with wear, they wouldn’t be very good engineers if they didn’t!

 

SO, at a certain rpm, the hall causes the ecu to misread – ecu shits itself and goes to last line of code – last line = max injector – too much fuel too early in the rpm means FLATSPOT!!!

 

This is why with a custom map you can mask the problem since the mapper can fuel "around" the instance of a flat. You still got the mechanical fault though.

 

make sense?? :roll:

[stevemac 0]

Sounds logical to me Captain.. :twisted:

[Dubcharged 0]

:lol:

[beavis 0]

Add to the equasion most G60 have a early retired Knock sensor and a wiring harness that looks like it has been baked in the fires of hell and back adds up to a recipe for complication.

 

VW were are very good at fail safing things, to the extent that many people drive around for years with a sender dead. The cars are down on power and underperforming, but, they do not act in any untoward way to make the owner notice there is a problem. Add a sensitive chip into the equasion and it just highlights the weak spots of the management.

 

The majority of tuners chips are 75% VAG origin maps with a few fueling and ignition points adjusted topend as so the extra air flow produced by a smaller than OE pulley does not exceed the parameters of the original map, so ultimatly the management behave in the same way as OE.

 

The problem raised its ugly head on my G40 as Bilal said.

Swapped the distributer over with the one of my other car and all was fine again, turned out to be a weaping oil seal causeing havoc with the disi's inside.

At 1st i'd discounted the distributer as there is a bill in the service history of my car from when it was in Germany from 2002 and only 40,000kms for a new distributer.

[Dubcharged 0]

The majority of tuners chips are 75% VAG origin maps with a few fueling and ignition points adjusted topend as so the extra air flow produced by a smaller than OE pulley does not exceed the parameters of the original map, so ultimatly the management behave in the same way as OE.

 

 

So you'd be paying for a standard chip with a few load points adjusted, partly the reason why they cant cope with boost over 1bar! AND also why they finish at 6200rpm which is where the standard code finishes.

[steveo29 0]

so whats the best fix...i.e cheepest??

[G60 0]

best and cheapest are not at all the same thing. especially on a corrado.

 

new hall sender :roll: ..new knock senser good idea too.

 

if you're going for cheapness, stick with the stock chip/setup.

[steveo29 0]

i didnt mean it as in "im a miser"....lets try again

 

where can i source the nesesary parts at a reasonble cost..im sure theyre avail cheeper than the dealer

[h100vw 0]

You could get a handful of 1800 digifant dissys from a scrappy and try them one at a time until you find a good one. Or bite the bullet and get a new one.

I got a brand new 2 litre 2E dissy from ebay for £10.52, with the cap and rotor.

Bargin.

 

Gavin

[dubster82 0]

new hall sender ..new knock senser good idea too.

 

but how mauch are these parts likely to cost?

[dubster82 0]

so not dear then :roll: :lol:

 

thought not.

 

Knock sensor though?

[leew 0]

If the dizzy is sending a signal to the ecu (which we know it is) then is there anyway the signal can be read and diagnosed?

[G60 0]

ive thought about this a little, only thing i would be worried about is interfering with a critical signal like that. i have heard of people hooking up an LED to see when the knock sensor is being triggered.. good idea!

[h100vw 0]

If you have a scope with a high impedance it won't interfere. I always slacken off and retorque the knock sensor on a service. If they are too tight they get oversensitive. I forget whether it is 10 or 15 lbft.

Gavin

[G60 0]

its 15Ib/ft.

 

i torqued mine down without a torque wrench, i'm sure i did it too tight and yes, it definitely makes it more sensative. i've heard of making up a 1" aluminum spacer to make the knock sensor LESS sensative, but i doubt this is a good idea. :lol:

[h100vw 0]

I'd say it's worth backing it off to see if it makes any difference. Doesn't cost much, unless you have to buy a small torque wrench to do it back up.

Gavin

[G60 0]

naw. car's parked. don't matter much now... was just to putt around, i wasn't goin for power numbers.

[Dubcharged 0]

Best thing to do is not to mess with critical signals. Torque up the knock sensor as directed by the book and let it do its job. If the hall is wearing out, replace it. dont try and intercept the signal since the ecu does rely on this signal.

 

You cant break the 100m record with a sprained ankle.

[leew 0]

Ok, so how do you know the hall sensor is wearing out...apart from from buying a SNS chip and seeing if it has a 5k flatspot?

[dubster82 0]

ahhh. lee, you've got it bud, its their sales angle!!! :lol:

 

 

:lol::lol::lol::lol::lol:

 

i know its not bilal :wink:

[stevemac 0]

Ok, so how do you know the hall sensor is wearing out...apart from from buying a SNS chip and seeing if it has a 5k flatspot?

 

Given the age of the G60's, and the cheapness of the hall sender (around £35 from memory) I'd just replace it anyway.

[Dubcharged 0]

ahhh. lee, you've got it bud, its their sales angle!!! :lol:

 

 

:lol::lol::lol::lol::lol:

 

i know its not bilal :wink:

 

Aaaaah crap, i've been found out!! :lol:

 

Its just one of those things, if you dont have a flat dont worry about it, if you ever get the car chipped to an aggressive spec then just take it from there.

[Sandy 0]

I am thinking about getting the SNS g60 stage 5 chip. IF I buy the chip I will take my C to Star Performance run it with my amd chip then install the sns chip if there isn't any improvement over my AMD chip can I return the sns chip for a refund ??

 

PS If I go ahead with this I will stick the before & after rolling road

printouts on the forum.

 

Sandy G60

[Dubcharged 0]

Well the dyno wont show you Digi-Lag - unless they hook up a wideband as well. If you have an A/F gauge then you'll see the difference. Dyno wont show you throttle response improvement as a result of No-Lag either, you'll have to use your butt dyno to feel it.

 

You also need to use a 3.5bar FPR with our chips.

 

Like i said, peak power may not increase, but the way it gets there on the road will!

 

Be interesting to see though!

[Sandy 0]

I've got an adjustible FPR on my C so thats not a problem. So could I return the chip if I don't feel any improvement in throttle response ??

 

Cheers

 

Sandy