M20B25 Rotex Converstion?

[Silverfang]

Considering i'm due to leave university soon, I'm already eyeing up the idea of wanting a bit more torque and BHP from the ol M20.

Now before i'd have considered tearing the engine out, selling it and dropping in a M52B28 or something along those lines.
However since the cambelt incident which resulted in this:



So since the engine's pretty fresh now, I considered the Rotex supercharger, having looked at Ant's conversion which apprently yeilds 290bhp on a stock engine, I'm rather interested in this!

Now the engine in question is a later spec low compression engine (8.8:1), bone stock with an ITG filter.
Now odviously, when swapping to S/C management would need to be replaced. But what else is required bar the supercharger kit?

From what i can guess:

> Fuel Pump
> Injectors
> Management (Emerald / Life Racing?)
> Intercooler.
> Various pumping.

I would also consider getting a decent manifold, probably from OZ Engineering (BTB quality, though might be cheaper!)

I'm just researching at the moment, but a supercharged Touring might be an interesting Q car
I would appricate what people's experience is like and is there any specific problems that require major re-engineering of the car.

[GeoffBob]

Appletree, Rix313 and Tim_Haynes all have Rotrex superchargers on their engines. Appletree and Rix313 on M42's, and Tim_Haynes on a M20B25, much like yours. Tim_Haynes' car, in the Motorsport section, will be most similar to what you are proposing, and I believe he is pushing around 320hp with his Rotrex C30-94 and race fuel.

[Kos]

I wouldn't pay much attention to some claimed tuners conversions as nothing is proven as far as I'm aware.

With 9 psi of boost from an eaton charger on a late spec a20b25, power made was 232bhp.

[GeoffBob]

I wouldn't pay much attention to some claimed tuners conversions as nothing is proven as far as I'm aware.

Not unproven Kos.



My apologies to Tim_Haynes for reproducing his Dyno graph.

With 9 psi of boost from an eaton charger on a late spec a20b25, power made was 232bhp.

Hardly surprising for an Eaton making only 9psi of boost. Eaton superchargers are of the type defined as roots pumps, and are notoriously inefficient, draining a substantial fraction of the engines net power, leaving a less than satisfactory amount at the flywheel to be put to useful work through the drive train.

Rotrex superchargers, on the other hand, are of the type defined as centrifugal blowers, and are vastly more efficient than a roots pump, leaving a greater fraction of the engines net power output accessible at the flywheel. With the correct choice of pulley sizes a Rotrex C30-94 will boost a M20B25 to 1.5bar (22psi) boost at 6000 rpm, inducting 34kg/s or air while making well in excess of 350hp net, at a cost of only 38hp lost to the Rotrex, provided the compression ratio and/or fuel octane rating are chosen such as to prohibit detonation, the intercooler provides adequate cooling and is non-restrictive, and the engine is sufficiently strong to withstand the rigours.

[Gunni]

34kg/sec ....

I don´t think so

That´s ALOT

I can see 0.35kg/s be a believable number

[GeoffBob]

34kg/sec ....

I don´t think so

That´s ALOT

I can see 0.35kg/s be a believable number

Well spotted Gunni . Purely a typo, I can assure you. Should read 0.34 kg/s, not 34 kg/s

[Silverfang]

GeoffBob, considering 0.34kg of air per second, using a fuel / Air ratio of 14:1, I would need an injector setup that'd deliver 0.0242 kg / sec of fuel or 1.46 kg of fuel per min.

Would Bosch Green injectors (I believe from a Escort Cosworth or Volvo 242 Turbo) cover this? I'm not familer as yet with which injectors flow what rates, but have read these are good for up to 350bhp.

[rix313]

That's alot of petrol Am I missing something or does that equate to 2litres of petrol a minute (petrol weighing roughly 0.7kg)?!

[Silverfang]

I believe this is at full throttle though Rix, but yes, that is a lot of fuel!

[GeoffBob]

GeoffBob, considering 0.34kg of air per second, using a fuel / Air ratio of 14:1, I would need an injector setup that'd deliver 0.0242 kg / sec of fuel or 1.46 kg of fuel per min.

Would Bosch Green injectors (I believe from a Escort Cosworth or Volvo 242 Turbo) cover this? I'm not familer as yet with which injectors flow what rates, but have read these are good for up to 350bhp.

Hi Silverfang,

Yes, at an AFR of 14:1 your engine will consume 24.28 mg of fuel per second, which equates to 1.46 kg of fuel per minute. I know its sounds a lot, but that's what it takes to sustain roughly 290kW (390hp) of net engine power (assuming a brake specific fuel consumption of roughly 300 g per kW hour for pump fuel). Please note that I say net engine power output. The power required to drive the supercharger, water-pump, alternator, cams and frictional losses must be subtracted in order to estimate the brake hp at the flywheel. A net power output of 390hp will realise roughly 340 bhp at the flywheel.

While it is possible, in theory at least, to dissipate this amount of power doing work against the combination of drive-train friction and aerodynamic drag alone, this would, in the case of an E30, occur at a speed well in excess of what would be safe for the car and yourself. Thus, The only time that you will ever see this sort of fuel consumption is during hard acceleration, or on the dynamometer. You must of course choose your fuel pumps and fuel lines to cope with the absolute maximum requirement of your engine. Two pumps would be a good idea.

Now, 1.46 kg/min equates to exactly 2 litres (2000 cc) of fuel per minute at a fuel density of 0.00073 kg/cc. Thus, your six cylinder engine will require six off 400cc/min fuel injectors assuming an injector duty-cycle of no greater than 83.3%.
At a duty-cycle of no greater than 74%, however, the 450 cc/minute Bosch "green top" injectors will work perfectly.

Regards
Geoff

[Ant]

Thanks for the never ending doubt Kos

323 crank/hp on R C30 - 91 on stock 8.8:1 CR @ 15 psi boost 65mm input pulley iirc ( a few years back now) inatke temps were 40-60 degrees C with and air/air IC setup

The development and R+D was split between A-Tech and Storm Developments on this BTW .I had alluded to a sleeping partner a few years back.

@ Geoffbob, cant argue with the maths dude 440cc/min are indeed the weapons of choice here, only issue is idle mix control @ sub 1K the inj are on min PW to achieve a stable 13.4 AFR idle mix @1050 rpms( used MS 1 ) Omex 700 series can go 0.6ms as min PW, MS 1 is 1.0 ms.

[Silverfang]

GeoffBob, considering 0.34kg of air per second, using a fuel / Air ratio of 14:1, I would need an injector setup that'd deliver 0.0242 kg / sec of fuel or 1.46 kg of fuel per min.

Would Bosch Green injectors (I believe from a Escort Cosworth or Volvo 242 Turbo) cover this? I'm not familer as yet with which injectors flow what rates, but have read these are good for up to 350bhp.

Hi Silverfang,

Yes, at an AFR of 14:1 your engine will consume 24.28 mg of fuel per second, which equates to 1.46 kg of fuel per minute. I know its sounds a lot, but that's what it takes to sustain roughly 290kW (390hp) of net engine power (assuming a brake specific fuel consumption of roughly 300 g per kW hour for pump fuel). Please note that I say net engine power output. The power required to drive the supercharger, water-pump, alternator, cams and frictional losses must be subtracted in order to estimate the brake hp at the flywheel. A net power output of 390hp will realise roughly 340 bhp at the flywheel.

While it is possible, in theory at least, to dissipate this amount of power doing work against the combination of drive-train friction and aerodynamic drag alone, this would, in the case of an E30, occur at a speed well in excess of what would be safe for the car and yourself. Thus, The only time that you will ever see this sort of fuel consumption is during hard acceleration, or on the dynamometer. You must of course choose your fuel pumps and fuel lines to cope with the absolute maximum requirement of your engine. Two pumps would be a good idea.

Now, 1.46 kg/min equates to exactly 2 litres (2000 cc) of fuel per minute at a fuel density of 0.00073 kg/cc. Thus, your six cylinder engine will require six off 400cc/min fuel injectors assuming an injector duty-cycle of no greater than 83.3%.
At a duty-cycle of no greater than 74%, however, the 450 cc/minute Bosch "green top" injectors will work perfectly.

Regards
Geoff

I'd agree with that GoeffBob , considering the BP figures. (I need to fish out my formula sheets again and do some math)
340hp considering drag issues sounds about right, so conisdering the setup might include a new exhaust manifold (OZ Engineering).

So by the looks of it, from this, I'd need the following:

Bosch 044 Fuel pump
440cc Injectors
New lines and regulator (for 3 Bar)
Intercooler - Saab / Volvo?
Pumping to suit

Would the stock fuel rail be suitable?

Ant: I would probably look at the omex or emerald setup to be honest, though can't argue with the MS1 setup doesn't work, just considering the car would be used daily so would like that lower idle.

[Ant]

dude you should have a stock 3 bar reg ??

Volvo and saab IC great for little ££ but an all alloy unit is sun £120 new these days so perhaps a better choice

044 or Walbro255, Wlbro cheaper by some margin last I checked though.

re management, I'd base that decision on location of your local tuner more than anything else TBH, Emerald and Omex both proven in this application , if you want some DIY input then you simply cannot beat MS , you could go the uni-Q route here with great success too.

150+ Mph in an E30 is interesting a house brick shouldn't go that fast !

[Silverfang]

Ant, I figured the stock one is good for 3 bar, but would it support the flow required? :s

Still 150mph in a E30 ... should be fun!

[Kos]

Thanks for the never ending doubt Kos

The development and R+D was split between A-Tech and Storm Developments on this BTW .I had alluded to a sleeping partner a few years back.

you're welcome Ant ( post edited, Names start with a capital letter ,Ant )

but what happened to that car?

re the eaton, consiering its a less efficient blower, a 50hp gain on 9 psi on a 150,000 mile bottom end is great result especialy as it was running stock "chipped" ecu with a rather prehistoric boost activated 7th injector.

it is a shame we dont see many well set up turbo and s/charged bmw's in the UK from the so called forced induction specialists.

lots of talk though.........

[Jhonno]

Still 150mph in a E30 ... should be fun!

Mine is fine at that speed.. Still pulling as well..

[GeoffBob]

@ Geoffbob, cant argue with the maths dude 440cc/min are indeed the weapons of choice here, only issue is idle mix control @ sub 1K the inj are on min PW to achieve a stable 13.4 AFR idle mix @1050 rpms( used MS 1 ) Omex 700 series can go 0.6ms as min PW, MS 1 is 1.0 ms.

Hi Ant, trust you are well.
Have to agree with you, Omex is probably best choice in the UK, although Appletree has just had good results with his Emerald. Down here in SA, Adaptronic and Autronic (from the land of Oz) have been well received and have more than sufficient PWM resolution to take care of idle on the larger fuel injectors, but these brands appear relatively unheard of in the UK, so probably aren't worth a look. MoTeC is of course an excellent choice if anyone can afford one.

[Ant]

@ Geoff, indeed geographic s dictate choice and all fine here mate.

you had anything to do with Dicktator ECUs ?? had one hhere for mapping( guy was from SA and taking car back ) SA domestic product iirc, quite a powerful bit of kit let down by god awful software IMHO

@ Kos, that car is fine thanks

re MS and PWM res its more to do with how the ECU reads the rpms, only 100 rpm res on MS1 out of the box, MS2 has 1rpm res, obv its all based on the calcs in the firmware.

@ Dan, 5 stud and wider track are defo worth the investment @ high speed

still dont like the 140+ bounce all E30s with stock track width are blessed with....

anyways enough OT

[Silverfang]

dude you should have a stock 3 bar reg ??

Volvo and saab IC great for little ££ but an all alloy unit is sun £120 new these days so perhaps a better choice

044 or Walbro255, Wlbro cheaper by some margin last I checked though.

re management, I'd base that decision on location of your local tuner more than anything else TBH, Emerald and Omex both proven in this application , if you want some DIY input then you simply cannot beat MS , you could go the uni-Q route here with great success too.

150+ Mph in an E30 is interesting a house brick shouldn't go that fast !

I'd not realised the alloy I/C market had come down so much in price, but will look into it once i've got work. As for ECU's, i think the Omex setup is done over at Northampton Motorsport, though i will have to double check.

Though the question remains about the stock fuel regulator and lines, would these be able to support the flow required?

There is another option as i do have the software for Life Racing ECUs (we use them on our FS cars) and have considered getting one of these installed, though would involve getting a loom made up.

Spare engine loom would be ideal as a template, along with an ABS loom, since the life racing can support Launch and Traction crontrol and the wheel speed sensors could be adapted to get this aspect working.

[Gunni]

If you are in Milton Keynes that is not so far from me in Marlow.

I´m going to reccomend VEMS yet again. It´s getting so damn good it´s just great for the price.
I have not had any form of issues with running 440cc´s with it at any idle mixture.

Also to note, the FPR only needs to remove enough fuel from the rail to maintain a set pressure, the fuel pump works with the FPR to maintain the regulated pressure, when the requirement goes up for more fuel at that pressure the regulator starts blocking off and the pump starts pumping harder.

The maximum return flow would be at idle IF your pump is pumping harder then it needs. Of course with a standalone you could always tune around this.

[GeoffBob]

[Ant]

I hear ya Geoff, it was an ultimately frustrating experience popped an MS1 on there in the end ( with JPT55 plug and play harness ) ran soo much better and 441 C/HP so Denim was a happy bunny

@ Gunni, you THE man for VEMS, and having used it I can say it ticks a lot of boxes, knock, EGT , cam synch and native sequential injector drives and Wideband 02 sensor , all good

Mr 'Fang could do a lot worse than pay you a visit

[Gunni]

[kingcruizer]

if your thinking of putting a rotrex on there....all i can say is do it. im more than happy with mine. a few teething problem but once cured she fly's. i have alot of fun with m3's etc etc
power wise, it's running 324bhp and does a standing 1/4mile in 12.4 @104mph.
traction is a major problem for me. even at the pod it spins in 3rd. not this year though as the new project has some w....i....d....e wheels which will help alot

thanks again ant

clive

[Gunni]

12.4@106mp?

That suggest not so much power but amazing grip of the line.

[Ant]

^ given the amount of MDF and subwoofers in the boot, that's V not bad Gunni

sorry Clive

[Gunni]

The speed doesn´t suggest enough power to get 12.4 without some SERIOUS grip of the line.

my friend on slicks got 12.04@116mph with a 1.7sec 60fet time. Which is very much inline with what e30´s do.

12.4@106mph is the same speed I did with my S50B30 cabrio but almost a whole second faster. Which does not make much sense.

[Kos]

The speed doesn´t suggest enough power to get 12.4 without some SERIOUS grip of the line.

my friend on slicks got 12.04@116mph with a 1.7sec 60fet time. Which is very much inline with what e30´s do.

12.4@106mph is the same speed I did with my S50B30 cabrio but almost a whole second faster. Which does not make much sense.

gunni, when you say a second faster i'm guessing you mean you crossed the line at 13.4 but some how clive crossed the line a second fatser with a similar termial speed to you in you s50 cabrio?

like you, what clive has said doent make sense , but a 13.4 @106mph would make more sence to me

every time i've been runnig a 13.4/5/6/7 i've been crosing the line about 106/5/4 mph in an e30

[Gunni]

I was actually running it at 13.27@106mph.

terminal speed is a great indicator of power while ET is a combination of power and traction.

Everybody I know who has run mid 12´s in a E30 has been running it at more then 112mph.

[kingcruizer]

sorry guy's my bad it was 114mph. ive still got the paper work some where.

and as ant said. i have a few amps and subs in the boot. but thats all coming out. my new project will be semi stripped out so i'll see if the times get better this year.