Marks RX7 - lets break a rotary.

[Steve Swan]

This tends to make me think that you hope this engine will be in to stay in, well for a while anyway....

 

[Mark Davis]

This tends to make me think that you hope this engine will be in to stay in, well for a while anyway....

It is my hope Steve yes, such significant investment this time with the whole set up so I’m somewhat confident it’ll last a little longer.

 

[cossie1]

It is my hope Steve yes, such significant investment this time with the whole set up I’m somewhat confident it’ll last a little longer.

Best not drive it though, just to be sure

 

[Steve Swan]

 

[Mark Davis]

Out with the accelerator cable and in with DBW.

Neat kit from Dorito Design.

 

[Steve Swan]

Now, am I correct in assuming that the engine's control system does not really consider you responsible enough to have the absolutely say on throttle position at a given time? In essence the ECU will check all the parameters, then look at what you have done with the throttle position (pedal pressing) and if what you have asked for is doable then it will happen, if not it will give you the closest alternative. This is meant to be a bit tongue in cheek, but I'm trying to understand the principles. I still use stuff that under performs or blows up if not used correctly. I can understand that at the specific output you are trying to achieve then this is the only sensible way, well, apart from a lottery win...,

 

[Mark Davis]

Mapper and ECU can do all sorts with DBW.

Limit torque/power, boost control, various safety features, (limitations on throttle position based on coolant temp, egts, oil temp) cruise control, launch control, safety for my water/meth set up, traction control.

Probably other things I’ve not thought of.
The Syvecs is pretty powerful in this regard.

 

[Duncan Grier]

While maybe other ecu's that have similar features the Syvec unit sure stands out for total control, saftey & features......just not cheap

 

[Mark Davis]

While maybe other ecu's that have similar features the Syvec unit sure stands out for total control, saftey & features......just not cheap

Yes I should say “other brands also available”

 

[Steve Swan]

I watched a fascinating little film on YouTube the other day, where they were testing different fuels on the same engine to check output. What they did not explain was if they changed the parameters, or if it all worked automatically. I assumed the Engine and it's control system was fully automated and could adapt in real time to maximise its potential . It was a Seat 2 litre turbo around the 460 BHP mark which was obviously quite clever full stop.
They did mention flex fuel and the tests using different fuels were interesting, although from worst E10 to best was only about 10BHP which to me showed the overall cleverness of the control system, without which it probably would have killed itself.
As a finale they went to about 30% ethanol and got over 500 BHP, though the engines fuelling requirement would have went up dramatically (meaning the system had plenty capacity)
The thing that struck me as odd was the operator/mapper was showing where the danger area was in the engine coming onto boost, rather than when the load was on proper higher up the range it was obvious on the ignition plots they showed.
This suggests a bit of a paradox in modern cars to me. My old rubbish is meant to work well at high rpm once in use it is never below 4000 rpm and usually not below 5000 rpm. Why build an engine that revs well, then want to do all your driving between 2000 and 3000rpm? Without specifically building it to work in it's defined range. It looked like it needed to have an incredible headline horsepower figure, but will never really be driven there.

 

[Adey]

I watched the same one @Steve Swan, the map was unaltered between runs but pushed the ignition timing a little, they run knock control/listening and pull timing as required (when it gets noisy), along with lots of other clever stuff. Pretty sure they did a different map with the spicy fuel though to show the difference.

10bhp was the peak difference but there was a big difference in drivability/mid rpm too, I think they highlighted this in comparing the ignition pull over the revs.

When a turbo engine comes on boost that's where there is a savage increase in torque and generally where things break. Atmo engines are very different and don't have a sudden increase/requirement/output of 300+lbft in about 750/1000rpm. Also the atmo engine works by sucking in air and blowing it out as you know, this creates a power band/best efficiency/power area especially when cammed and built. Meaning that they behave dead below certain rpm but are great on song at high rpm (or where designed to perform). An air compressor can cover that gap easily and basically cram air in at all revs. They still come into their range though and as they come up tend to bend things. I think the main thing is, they are road cars, not race cars. So the 450+bhp works well all around and from a manufactures point of view give drivability at all revs, yours is built to be a race enging and be driven balls out all the time, no need to worry what its like in traffic on the way to Tesco's.

The rotary is a different beast again

 

[Steve Swan]

Thanks @Adey that fills in some of the blanks. Fuel is an interesting subject, would have been good to see what it would have done on more Dope, but the injectors will have a limit and i think they were probably plus 15% on fuel @30% Dope. Was noticeable how the Meth lowers knock potential and helps cylinder cooling, but that's 1920's tech really. I just think lots of people get lost (including car makers) in what they want to achieve. Why have that massive engine breaking step (as well as the driveline)when you could sweeten it out, less headline horsepower yes, but much more driveable (and ultimately quicker too)

Apologies for the hijack. I always watch this thread from an Academic/learning standpoint as it covers lots of points that I may never use, but are interesting to understand. It's also fantastic when it's not your own money that is being consumed in the process. @Mark Davis hopefully not yours this time..
What about Nitromethane??
I'll get my coat.

 

[Mark Davis]

I’m going to be running direct port water/meth set up 20/80 water/meth. Should see an octane boost up to 105 mark. So you get the fuelling octane boost and the cooling capabilities to keep knock at bay.

That’s the theory anyway.

Here’s a similar set up to mine albeit twin turbo. This is a semi PP engine too. It’s one of my tuners customers cars.



Made just over a 1000 at 34psi.

I have flex fuel but too for E85 but the practically of it holds me back so using a water/meth guru is hopefully the key.

In the end the above set up bent the e shaft ( crank) so won’t push that far but shows what is capable on a little 2 rotor. 2 rotors less than Dahm and almost same power.

 

[Mark Davis]

The joke is the Aussies were doing this 5 + years ago. Nobody does anything like this over here. As you all know from my experience hard enough keeping engines alive at baby boost on pump fuel in UK

 

[Steve Swan]

Quite incredible really. It's like the missing link between reciprocating engines and the turbine it has elements of both.

 

[Steve Swan]

A guy in Oz used to send me the occasional Fast Fours and Rotaries mag back in the late Eighties if it had a Renault feature. Ozzies always been mad for Rotaries. Maybe they never had the RO 80

 

[DaveL485]

What about Nitromethane??

As much as we'd all love to be amused by the expected explody kaboom, I suspect it'd be boring - I doubt it'd even run given that you need to hoof in eight times more fuel with nitro than you do with pump gas, IIRC stoich is 1.7:1 over the 14:1 for gas.

Even more boringly, you can't even mix a bit of Nitro into petrol, it'll just sink to the bottom. You're better off using a Nitrous kit, it's very similar chemistry delivered in a different way.

If you want to add some fun in your tank lob in a 20% mix of Toluene.

 

[Steve Swan]

Having to stop and fill up the tank every every 4 miles or so would be restrictive. Fun while the money held out.. normal to cut nitro with Methanol .. Oh.... Wait.. This is where I came in............

 

[DaveL485]

Having to stop and fill up the tank every every 4 miles or so would be restrictive

I suspect Mark will be filling up around this regularity anyway looking at the spec LOL

 

[Mark Davis]

A few shots from Anil, look at the state of the bay. It’s going to look great and add a lot of value.