48 replies to this topic

[shaddy]

i've just bought a complete engine with rotrex supercharger. (for the charger only) well unless the engine ends up being something special. the engine has had some work done to it, head has been ported double vaule springs etc, unsure of the engine spec yet as i've not taken it apart, believe it to be a 1275 but i could be wrong.

i also have a 1360 engine with a well ported head double value springs etc, and i was thinking about fitting the sc to this engine.

now i have a few questions.

what is the best cr when using a sc i have read somewhere that with rotrex sc the cr can be higher than normal is this correct?

how do i also calculate the cr.

some other points i need to consider,

what ratio diff shell i use?

cam choice? i know the 1360 engine has a mini miglia cam fitted is this to much

other info that may help people's comments the car will be fitted with sccr box and sc drop gears and will hopfully be used in some hill sprints etc so drivability around town i'm not bothered about

[Wil_h]

Rotrex superchargers are a cunning mix of a turbo and a supercharger. Unfortunately, they take the worst bit of each. i.e high boost threshold of a turbo and high power consumption of a supercharger.

You are right about the CR though. Because of the high boost threshold you can run a higher stactic CR as you wil only make boost at higher revs where the dynamic CR is lower. Would need some thinking about to optimise it.

The idea of the rotrex is that it can easily be bolted on a standard engine, making boost at high rpm only.

Will be an interesting project, and I'd be interested in the results.

[shaddy]

what sort of cr are we talking about, say a normal sc runs a cr of 8:1 ish and a high end na runs at 12:1 ish. would somwhere in the middle make for a good compremise for getting the most out of the sc. the cam choice will also play a big part into the overall permofamce can any one suggest one?

hoping to take a look at the engines to see what i've got this weekend

[Wil_h]

It's a good question. Assuming you use it blow through and have a decent IC then 9 to 9.5:1 with 10 or 12 psi should be fine with a decent ignition map. It looks like it may be possible to run higher, but as I say it would need thinking about. Unlike a turbo it won't reach max psi at say 3500rpm then stay at that psi to max rpm, but it'll have a gradual build up of boost. Hense why you can run higher CR.

You could plot RPM vs. boost on the compressor map based on the airflow requirements as the revs build up. Then you'd know what the boost build up would look like. This is obviously dependant on the pulley size, but I guess you'd choose this first based on the maximum boost you wanted at max rpm.

And yes cam choice is important. I'd be tempted by a 276 as an experiment, but an Avonbar phase 2 would probably be a more sensible choice as a start.

The above is all theory of course, I have no practial experience of the rotrex. I have looked on the rotrex website for info, it has compressor maps, but no details on drive losses, which I find interesting.

[shaddy]

It's a good question. Assuming you use it blow through and have a decent IC then 9 to 9.5:1 with 10 or 12 psi should be fine with a decent ignition map. It looks like it may be possible to run higher, but as I say it would need thinking about. Unlike a turbo it won't reach max psi at say 3500rpm then stay at that psi to max rpm, but it'll have a gradual build up of boost. Hense why you can run higher CR.

You could plot RPM vs. boost on the compressor map based on the airflow requirements as the revs build up. Then you'd know what the boost build up would look like. This is obviously dependant on the pulley size, but I guess you'd choose this first based on the maximum boost you wanted at max rpm.

And yes cam choice is important. I'd be tempted by a 276 as an experiment, but an Avonbar phase 2 would probably be a more sensible choice as a start.

The above is all theory of course, I have no practial experience of the rotrex. I have looked on the rotrex website for info, it has compressor maps, but no details on drive losses, which I find interesting.

i will look into the compressor map see what i find, i must say its all new to me as well, i'm working on all theory at the monment. i think the ic will be a must also.

your rised another good point ignition map something elae i need to look into,

[shaddy]

finaly got round to stripping the engines

couple of questions

ae 212 51 +0.60 cuf pistons do these have 12cc dish

others are trw-175-9335 0.30 what cc are these

need to confirm these then i can start working out the cr

what is the standard thinkness of a 12G 940 head? i think one of them has been skimmed

[AndrewJ530]

I think i've read all heads start out at 2.75" in depth. Someone will be able to confirm it on here though.

[MIGLIACARS]

here is a picture of my rotrex supercharger conversion

[MIGLIACARS]

here is another

[Wil_h]

Looks a nice install, 8/7-port head on throttl ebodies, very slick.

I presume it's in a Metro. What do you plan to use it for?

I was going to ask about performance figures, but it seems to be missing lots of bits.

[shaddy]

that looks a very neat set up i dont think mines going to look anything like as good as that

what bhp will you expect from that?

also have you had many dealings with the rotrex i'm new to all this so any advise would be most helpfull

[MIGLIACARS]

[quote name='Wil_h' date='Dec 28 2009, 04:25 PM' post='1682323']
Looks a nice install, 8/7-port head on throttl ebodies, very slick.

I presume it's in a Metro. What do you plan to use it for?

I was going to ask about performance figures, but it seems to be missing lots of bits.


hello
yes it a 7 port head, yes its in a metro, i use it as a curcuit racer,
performance as a n/a 5 port racer it was very quick, check it out on youtube

Croft metro incar race footage 2007 august z cars
so now with the extra power and tourque it will be even better.

we have decided to limited to power to around the 170-180bhp to give the gearbox a chance, there is protenial for 250bhp but the transmission will be the weak point.

[MIGLIACARS]

.

Edited by MIGLIACARS, 24 September 2016 - 07:46 PM.

[MIGLIACARS]

and another

[shaddy]

that looks very well engineered did you do that yourself?

what is the blue take off for?

i was thinking off similar idea for the mounting of the sc, the oval holes are they to allow you to tebsion the belt