Author Topic: LL's Mk3 1.8t Cab  (Read 430121 times)

Offline topher

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i've never seen any detonation incidents with qpeng stuff, but you should probably stick an AFR gauge on your list of bits to buy.

Offline LazyLunatic

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i've never seen any detonation incidents with qpeng stuff, but you should probably stick an AFR gauge on your list of bits to buy.

Ben did say that he had not seen anything like it. it makes sense that you would need to stick to what the ecu has been mapped for, i.e. 97 octane fuel.

yeah its on there, takes priority over all other gauges. although afr is the only one i have thought about fitting first. boost, etc might go on afterwards, but its finding the space to put the gauges.

cheers :)

Offline Diamond Hell

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Ben did say that he had not seen anything like it. it makes sense that you would need to stick to what the ecu has been mapped for, i.e. 97 octane fuel.

So what happens if you get a duff batch of fuel, that's only 95RON?  You can't control that and that is why engine management systems run knock-control as a feedback loop on the ignition map.

Remember this is something that can take seconds to destroy your engine.

I cannot believe that despite no knock control there have been no detonation-grenaded motors running QPENG. 

It's missing a major safeguard that pretty much ALL manufacturers use on their cars.  It's so important that (as an example) the ABF uses two knock sensors so it can accurately control the ignition advance.

Also, what happens if you rock up at a petrol station to find they only have 95RON on tap and you're running on fumes?

An AFR gauge won't tell you about detonation.  That's what knock sensors are for.  An exhaust temperature gauge might help, but it happens so quickly it's all over and done before you can respond to the gauge.

The only way of avoiding it with static ignition mapping is to run a massively conservative map, which will compromise power hugely.  Even then, it's still a big risk to take.
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Offline Wayne

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Ben did say that he had not seen anything like it. it makes sense that you would need to stick to what the ecu has been mapped for, i.e. 97 octane fuel.

So what happens if you get a duff batch of fuel, that's only 95RON?  You can't control that and that is why engine management systems run knock-control as a feedback loop on the ignition map.

Remember this is something that can take seconds to destroy your engine.

I cannot believe that despite no knock control there have been no detonation-grenaded motors running QPENG. 

It's missing a major safeguard that pretty much ALL manufacturers use on their cars.  It's so important that (as an example) the ABF uses two knock sensors so it can accurately control the ignition advance.

Also, what happens if you rock up at a petrol station to find they only have 95RON on tap and you're running on fumes?

An AFR gauge won't tell you about detonation.  That's what knock sensors are for.  An exhaust temperature gauge might help, but it happens so quickly it's all over and done before you can respond to the gauge.

The only way of avoiding it with static ignition mapping is to run a massively conservative map, which will compromise power hugely.  Even then, it's still a big risk to take.

Spot on you need to run a knock sensor really.

Offline Jay

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I was going to say the first gauge you would need is an  EGT gauge , but DH got there first  :wink:  This is the FIRST gauge the IDI diesel boys add.

DH you have PM about knock sensors and Diesels  :wink:
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Offline LazyLunatic

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ok looking into it a bit more, and found that some tvr's run the mbe ecu, same as what qpeng use. now the mbe ecu doesnt use a knock sensor. although this increase performance, seeing as a knock sensor detunes the engine when needed to reduce pinking and stop it from blowing up. as long as 97 or higher octane fuel is used, then its fine.

it sucks down here, nearest 99 to me is like 20 miles away, which is v power. supposed to be the best 99, although many say tesco 99 is better, but there is no tesco 99 near me at all. so i will run the next best thing - BP ultimate (97), which is like 1 mile from my house.




Offline Diamond Hell

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ok looking into it a bit more, and found that some tvr's run the mbe ecu, same as what qpeng use. now the mbe ecu doesnt use a knock sensor. although this increase performance, seeing as a knock sensor detunes the engine when needed to reduce pinking and stop it from blowing up. as long as 97 or higher octane fuel is used, then its fine.

You really are missing the point.

Just because certain TVRs have run no knock sensor doesn't make it OK.  I say again - turbo engines are more prone to knock.  I don't think any of the TVRs would have been turbocharged.  Your engine is far more stressed and likely to encounter this issue.

By all means go ahead with what you're doing, but you need to understand your car will be missing a major engine safeguard, used almost universally in modern engine management (even back to Golf2 Digifants).  These guys haven't been fitting the knock sensor for fun.

One tank of 95RON fuel, or even a poor batch of +97RON might well kill your engine.  I know that's not a risk I'd be interested in taking and I'm running a cheap engine!

You'll note most cars don't have a shift light.  That's not really on the radar for anything but a rotary, yet QPENG seem to think that's more important than a knock sensor.  Go figure.
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Offline Wayne

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^^As above you need something to safeguard the engine, a knock sensor could save you a lot of trouble and money in the end.

Offline LazyLunatic

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yeah ok, i understand the point you are making, you have said it a few times, but the point im making is there isnt a lot i can do about it..... im not going to change management, not at this point, and i take it a knock sensor is built into the ecu so it cant just be "added" .......

its all very well picking out flaws, but if i cant do anything about it, then thats that.

cheers :)



Offline Diamond Hell

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i take it a knock sensor is built into the ecu so it cant just be "added" .......

Correct.

its all very well picking out flaws, but if i cant do anything about it, then thats that.

It's not picking flaws.  It's a raging gurt black hole.  There are two systems to protect your engine - lambda and knock sensor.  They control the key variables in the system.  You've cut out 50% of that control. 

As a comparison you have two modes of expelling waste from your body.  If you lost control of one of those, would you be happy with things, or think it was a minor flaw?

I think buying a proper management system straight outta the traps would have been the best idea.  You're at the point where the system isn't in the car.  It's my view that now is the right time to swallow your pride, sell it on and get a proper management system (one with sphincter knock control, for a start). 

Lads on E38 go nuts for QPENG - put it up for flog on there.  They're dying to spend money replacing their engines regularly (it blew up because a deer ran out in front of it and got sucked in the mad intake system, innit. I haz got the new one chromed inside etc). 

I don't think you are quite so keen on replacing blown up engines, are you?
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