E10 engine knock

[MX-3fan]

So I don't usually use this fuel for obvious reason, but occationally you're out somewhere and asda is the only place that you can get to.

Does anyone else have engine knock when using E10? All our cars seem to be very different when it comes to fuel, but mine absolutely hates this stuff. Even adding octane booster seemed to do nothing for it. Once i'm above 5k it knocks like a jehova's wittness! Should I dump a load more 2 stroke in there to try and help, or just run it down low and fill up with premium?

Mainly curious to see whether others have had issues with this stuff

[Conan]

If an engine has been run on premium fuel for a long time then it gets used to it ( we call this engine conditioning )
When you condition an engine to run on high grade fuel it will not like going to low grade fuel ( who can blame it )
It is possible to condition the engine to run on low grade fuel by slowly adding ever increasing quantities of low grade fuel every time you fill up ( it could take some time )
This is why people have different experiences with different fuels a lot of the time.
Just top up with some good stuff and see
Regards
Pete

[MX-3fan]

It's not unusual for some owners to report rough running with standard grade supermarket fuel, and a noticeable improvement on higher-grade, especially Shell V-Power and the like.

The mechanism is unclear because, unlike many high performance engines, the Renesis PCM doesn't try and creep the ignition advance to increase power, until the knock sensor tells it to back off.

Rotary engines gain very little (if any) increase in power by advancing the ignition, while they can easily be totally destroyed by pre-ignition detonation. So the knock sensors job is a safety net and can trigger limp mode.

Basically the Renesis isn't programmed to run any differently with different fuels.

This has been happening long before E10 (or even E5) was introduced.

The first sentence says "some owners" because others report no noticeable difference at all between fuel grades.

[MX-3fan]

Ahh that does make sense. I have used tesco 99 since I bought it. I'm truly amazed at the difference. I certainly won't be using it again unless I really have to. Thank you for the explaination

[RenesisRaceBuggy]

Could be the E10 cleaning built up crap/oil off the walls causing it.

[Paul_13]

I can't run my stagea (rb25det) on e10 it will not accelerate at all on the stuff.
Such poor quality fuel

[PaulAV]

I have in the past experienced poor running in Asda fuel although I never use "the good stuff" I think it's an Asda fuel thing, if anything knock might be reduced running that much ethanol as the octane is increased and combustion temperatures are reduced with ethanol compared to 100% dinosaur bones

[MX-3fan]

Does anyone know how they're selling E10? If the octane rating rises with bioethanol, does that mean that they're using a lower grade fuel, lets say 92, boosted to 95 with ethanol? I'm sure if it were 95 + ethanol they would happily advertise it as a higher octane (and sell it for even bloody more!). Just trying to make sense of it all.

Either way, my car hates it so I won't be using it unless it's an emergency.

[PaulAV]

Ethanol would make up part of the octane modification, so whatever they use to increase octane would be reduced slightly to accommodate the increase in ethanol(small percentages)

[New Duke]

Does anyone know how they're selling E10?

It was discussed here when E10 was introduced that it also provides lower mpg than premium/super. To the point of generally cancelling out the cost saving. That depends on a few variables and is different depending on the car, but it stands in principle.

But essentially the whole 'it reduces CO2 emissions' claim that pushed it's introduction was a con as you need more of the stuff to travel 'x' distance. So now instead of regular E5 we now have E10 that conveniently is more profitable. Progress!

[Milos_Balunovic]

New Duke. Yes same CO2 emissions but very diferent other emissions like NOX, CO, etc...

Re "car conditioning". No none of the vehicles are built to do that. That would require highly advanced auto tuning features.
And knock is insufficient to be the monitor as beyond MBT you lose power and start destroying the engine even of ist not knocking!

The most that the cars do have is that they have a max advance from which they back up in case of knock detected. That is done seamlessly and is more than sufficient to account for bad fuel.
Rx8 oem ignition table is ok to run with average fuel quality. If there is some very bad mix it will just retard the ignition by 10deg and "ride on the knock" sensor. No errors or limp mode will be triggered. A lot of tuners over doo the ignition timing and than with any fuel that is not fresh it rides this knock table. While some countries have good fuel and the 95 is sufficient to advance few degrees without such problems.

Also ECU will create fuel trims in matter of seconds to compensate the now "lean" mixture.

Your car is not knocking becouse of bas fuel, but rather something else and I would try to investigate that.

Bad ignition can be often missinterprated as knock as the engine cannot properly burn ......

[350matt]

I'd agree with Milos

it should run just fine on E10

when did you last replace the plugs and leads ?

[MX-3fan]

Plugs and leads are under 10k, coils are d585, but same thing with stock 'c' coils. It only happens with e10. Very peculiar. Perhaps the walbro fuel pump I installed, although that it unlikely?

[warpc0il]

Mine definitely runs smoother and is more responsive on premium.

The difference is subtle but noticeable, even for the passenger.

For example when we drove from Essex up to Scotland, for the ferry over to NI.
We left with a full tank of Tesco Momentum.
At some point on the journey, with a near empty tank, we filled-up with random "95".
Within a few miles the engine felt rough, not misfiring or anything specific, just not silky smooth, but we both noticed.
The next refill was Shell V-Power and it only took a few miles more for that silky smoothness to return.

This wasn't a one-off experience, just the most obvious.

The car has done 20k miles and many track days since, with that same ignition system, just replaced the plugs today and they're perfect.

The nearest equivalent I can think of to the change in harshness was when driving a members car where he'd locked the joint between the back of the cat and the catback solid. We cleaned-up the joint, fitted a new donut seal and springs, so the two elements could move more independently. His reaction to the change was "WOW".

[Milos_Balunovic]

Do you have your car mapped? I wonder if your maps (if the OP also has his car remaped) is that the knock retard strategy is changed to non conservative value. Either I was so lucky never to fill up that of a bad fuel (doubt it) or the car behaved normally. Im ofc speaking of normal driving. When you push it full throttle high in rpm the quality will show but not near as noticable as you guys describe it.

[MX-3fan]

I'm unsure if mine has been mapped to be honest. Certainly not by myself, but it did have the d585 coils on when I bought it so it could have had a mini map for dwell, but as said the same thing happens on the genuine 'c' coils. Filled up with some tesco 99 today and it sorted it right out. Very strange stuff. The compression is bad but I don't think it would cause these issues only on a specific fuel lol

[RenesisRaceBuggy]

Mine definitely runs smoother and is more responsive on premium.

The difference is subtle but noticeable, even for the passenger.

For example when we drove from Essex up to Scotland, for the ferry over to NI.
We left with a full tank of Tesco Momentum.
At some point on the journey, with a near empty tank, we filled-up with random "95".
Within a few miles the engine felt rough, not misfiring or anything specific, just not silky smooth, but we both noticed.
The next refill was Shell V-Power and it only took a few miles more for that silky smoothness to return.

This wasn't a one-off experience, just the most obvious.

The car has done 20k miles and many track days since, with that same ignition system, just replaced the plugs today and they're perfect.

The nearest equivalent I can think of to the change in harshness was when driving a members car where he'd locked the joint between the back of the cat and the catback solid. We cleaned-up the joint, fitted a new donut seal and springs, so the two elements could move more independently. His reaction to the change was "WOW".

A couple of premium fuels have small amount of lubricant, could be that which changes the feel, especially in an RX8. Be interesting to see if you feel supermarket 95 with a touch of quality 2T feels the same

[350matt]

Agreed both Tesco 99 and Shell V power have lubricant in them to reduce friction, higher octane will slow down the combustion and improve it
especially on an engine with poor combustion

I tend to run 95 with some 2T premix most of the time and when I do treat it to premium ( mainly as an experiment to see the difference in mpg) there is a small improvement in engine smoothness

[Steve.82]

Also ECU will create fuel trims in matter of seconds to compensate the now "lean" mixture.

Yep, in bits of the map, load and throttle where it's allowed. I never predictably figured out how any trims effected open loop portions of the map(s), if at all, so I gave up in the end and just tuned the whole lot to work open loop with datalogging and run a Wideband to keep an eye on it. Stock runs so rich the open loop bits are still way too rich even on E10...

It seems a lot of reasons the Renesis is frowned on a bit are based around high temperatures around the port. More ethanol means you can run lower AFR for the same lambda and therefore cooler, at the cost of higher fuel consumption. Mine lives on E10.

[Milos_Balunovic]

The LTF stays on in open loop and efects it directly. STF is ofc only for closed loop. Now what LTF is actually used at each open loop position I dont know but its loggable so it was easy to follow. When testing the 1.12 lambda as the most optimal for low consumption up to some 50% load i had to do it all in open loop as closed loop didn't allow past 1.05 no matter what. And than I allowed closed loop only on idle to make sure a failing injector wont fry my engine.

But regarding fuel and stoich in ECU. I remember (could be wrong). That ECU uses 13.something:1 and not 14.7 as stoich afr. Which is closer to e10 than one would beleive . Thats way on e5 or clean you get most of the VE table close to 100% and good amount above it (yes renesis has fancy intake but it cannot be that effective at alll existing rpms and loads)

[mi60o0]

All my cars live on e10
We had e10 and more in Bulgaria for years
We do have few lpg rx8 to in Bulgaria rx8 group
I put premium every 3 tanks
My Lexus haven’t seen premium with 84 litre tank

[Milos_Balunovic]

Liquid LPG would be best for a wankel. No carbon deposits, iat cooling etc

[warpc0il]

We had three members with dual-fuel LPG 8's on the forum 10 years ago, though I'm not aware of any still running in the UK.

One of the problems, that a friend with a dual-fuel Range Rover is struggling with, is that most filling stations that used to offer LPG on the forecourts have converted that space to EV charging, and both Calor and British Gas no longer allow retail access to their depots.

This is also an issue for motorhomes that converted from replacement bottles to fixed refillable gas systems.

[mi60o0]

We had three members with dual-fuel LPG 8's on the forum 10 years ago, though I'm not aware of any still running in the UK.

One of the problems, that a friend with a dual-fuel Range Rover is struggling with, is that most filling stations that used to offer LPG on the forecourts have converted that space to EV charging, and both Calor and British Gas no longer allow retail access to their depots.

This is also an issue for motorhomes that converted from replacement bottles to fixed refillable gas systems.

The reason why I haven’t converted the v8 yet in Europe main land is easy on lpg but uk is a struggle