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MG MGF Technical - Rolling Road Results

I've just came back from my rolling road session. Results were encouraging. Figures were 125BHP@ 5450 RPM and torque was 127 Lbft at 3000 RPM. That means an increase of 7 BHP over standard and 5 Lbft of torque. Not a bad result for a 30 K&N panel filter and my modified intake pipe. ;-)
Bob Millar

Are you using the Rover Specs as Reference to compare or is your reference the result of a prior Rolling Road test (without panel filter and without rerouting) ?


Where did you go and how much did it cost you?
David Clelland

> Are you using the Rover Specs as Reference

Unfortunately yes. I didn't have it rolling roaded in standard spec.

> Where did you go and how much did it cost you

I went to Stathclyde Auto Clinic in Irvine. It cost £40 per hour and it took about an hour as I got quite a few runs on it.

Bob Millar

Bob, the figures look good. :o)

Bob, picking up on Thierry's point, and probably just re-iterating something you already know, production engines vary by about ±5% because of production tolerances. Because of this, on a K-series with a quoted output of 118 bhp at the flywheel, you get a range of 112 to 124 bhp. So this means you could be either over or under-estimating the gains you are getting from your modification...

Still, 125 bhp is an excellent figure - and should encourage others to perform this excellent mod.

How does the car feel on the road?
Rob Bell

A lot more responsive and less hesitant low down. Foot down in 2nd gear at about 15-20mph results in a much quicker pick up. There was always a seconds hesitation before. One thing I did notice from the graph though was that the torque curve dip circa 3000rpm wasnt eliminated but torque was higher than standard at this point anyway.

Certainly bodes well for the future. MOT due next week and after that the CAT is coming off & a 52mm throttle body as well (funds allowing). I spoke to the guy at the rolling road about these FSE boost valves. He's fitted them before and claims that after they've been set up properly he's seen gains of up to 5 bhp and it doesnt only benefit those with head work.

On a side note, it was bloody scary watching the car on the rollers. You never appreciate just how fast your wheels are actually turning when youre driving & the noise was unbelievable. The speedo on the machine was indicating 100 mph at one point. Had horrible visions of it jumping out the rollers and smacking into the wall!!!
Bob Millar

Don't expect massive gains from the 52mm Dell'Orto throttle body Bob - but the gains in torque and driveability make the modification well worth while :o)) The car will feel great afterwards... :o)

Removing the catalyst has no performance benefit (see for the results of Paul Sharpe's organised tests) - but if you are doing it for the sound, then hey, why not? Just remember to replace it for the next MoT! ;o)

The FSE power boost valve... hmm - been discussed many times here. Broadly speaking, the majority of opinion is that these devices don't do much for power, but again are reasonable for fast throttle transients. Worth the cost of purchasing/ fitting/ fettling? Only you can decide on that one. :o/
Rob Bell

I'm not necessarily interested in massive horsepower. The car has more than enough for my driving ability. What I'm more interested in is getting the most out of the car be it improved throttle response, driveability etc.

Anything which eliminates the compromises MGR had to make when developing the car is a bonus.

Any yes the only reason I'm going to ditch the CAT is purely for noise reasons! Although looking at those CAT tests the CRP did offer some BHP gains (+3 if I remember)
Bob Millar

Bob, perhaps the biggest compromise on the car, after the air filter arrangement, is the design of the standard exhaust manifold.

It is not the greatest design in any case, and for manufacturing ease, is welded circumferencially from the inside: the weld often resulting in signficant impairment of exhaust gas flow, resulting in higher than ideal back pressure, and ill-timed exhaust pressure pulses...

Although it has not yet been independently tested, the Janspeed exhaust manifold sold by Mike Satur is going to be a very sound investment (no pun intended). There have been a series of very positive reports from owners, and the kit is a superb bit of design. For the cost of a s/s exhaust system, you get more benefit.

Personally I'd get one of these before the cat bypass (+3 bhp, but -1 lb.ft) and FSE power boost valve. :o)
Rob Bell

Re the manifold I've heard people saying you can grind an internal weld from the manifold giving more airflow.

For the moment I'm really only concentrating on mods I can do myself as the car cant be off the road for any length of time. It's my only car and I have to commute everyday.

Perhaps I could source a manifold from a scrapyard and do the grinding myself.

Does any K-series manifold fit the MGF. I assume the only real difference is from the flexi hose section on but I may be wrong.

Although in saying that Im reluctant to undertake a manifold removal myself. I had a nightmare of a job on a Pug 309 GTI (I know, the shame) that I used to own. Managed to shear a manifold stud off when replacing it once. Disaster! Had to drill out the offending stud etc. And I'd been very careful when I was doing it. Plenty of time taken and penetrating oil, a bit of heat etc.

You learn from you mistakes I suppose ;-)
Bob Millar

Hi all,
if you intend to get the modification done to the existing exthaust mainfold - be sure that as much as possible of the outside circumference is firmly welded before any attempt to remove the inner weld !
Otherwise it will be too little weld material present and cracks and blow-by will turn up in no-time. Know from experience the hard way ! Totally agree with Rob that it is a wortwile mod. maybee even more now when there is a bolt on alternative... Anyway, funny that those small inside welds has such an big impact, the diff. to an otherwise "fully loaded" (FSE, airbox, big bore TB,sports exth. etc.etc. )car is clearly felt in better torque all along the rev-range.

BR, Carl.
Carl Blom

Carl: Sorry for highjacking the thread, you have an FSE fitted ? If so can you either comment here or over email over your experiences and how you configured it correctly ?


weren“t you to supply a RR with your PBV fitted, or was it someone else?


T, I was walking more or less in the dark until i fitted a second cheap lambda sonde in the bypass tube and a homemade LED bar-graph that could be viewed from the drivers seat.
When I had all my mods done (except the FSE) there was a a lack of power at high speed down the long straights on the track (especially with hood down).When letting of the accelerator slightly there was a felt surge in power ! This made me assume that the engine now was running a bit lean ,at least at this specific type of driving. Connections to the original "on-board " lambda sonde did not reveal any such problem.Healthy figures in the 900mV range was present. What I didn“t know then was that this was NOT the actual lambda value but an inserted voltage from the MEMS !! Still not satisfied I welded a nut into the bypass tube and fitted one of those one-wire cheap sensors that are avaible over here. Now the full story was told, car was running OK at all times exept at full throttle in high gear / full speed. Not running lean directly but very close, values around 400 to 480mV was recorded. By fitting the FSE and slowly increasing the adjustment up to approx. 3,3 Bar I had something close to 900 mV at full open throttle and full load. I know well about the restrictions of voltage readings from a lambda sonde but at least this was as close as possible to real life.
It was interesting to note that adjustments had to be made at max load = hood down at speed.
Hope this can be of some help. Dont think that everyone fitting a FSE need the above procedure ,I just wanted to still my curiosity...
PS. My valve was a bog standard FSE NOT made for the "F" ,probably there are also tuned ones for at least every size or type of engine when ordered.

Sorry for the lengthy post, BR , Carl.
Carl Blom

Thanks for your valuable comments on this. I wanted to tell everybody (and perhaps you if interested) my findings when trying to find out how to setup the FSE (on a standart car running normaly - not lean like yours) "correctly". I would be happy if somebody can point out a mistake if any.

A FSE (PBV) Dealer told me this :
You have to measure the pressure on the standart boost valve using a Manometer (Measures pressure), then install the PBV and using the Manometer add 0.3 - 0.5 bar on top of the standart value. That would be everything there is to do.

Any comments on this will be greatly recevied as I have to setup an PBV in the weeks to follow.

@David, your correct that was me:

My plan for the RR :
- Trophy standart
- Trophy with TF KN57
- Trophy with TF KN57 + PBV

Currently that would cost me arround 300 Euros, I'll try to make a deal with the RR owner, becuase frankly that is too much.

I am prepared to contribute a little. the BPV has been too much a subject of suspicion. It has to be cleared out what its benefits are!

Anyone else wants to join?


I contacted an other dealer capable of doing RR sessions, the prior one (NCM.LU, pun intented) wasn't even willing to do a RR although they advertise it as a service on their site and want 100 Euro per session.

Bottom line: I will get in touch with people who know everything abut fuel injection systems and how to set them up, they mainly have all Bosch systems on this planet to do so :) Hopefully the price is ok too and I can get a bit of information on how to set this up correctly.

Exhaust Manifold:

Bob, I agree completely with Carl's warning - ensure that the pipework remains intact after grinding - a few external welds may be necessary (at bit of MIG welding - should be straightforward).

Regarding the changing of the exhaust manifold - actually, that job *shouldn't* be too difficult. Lots of penetrating oil and some elbow grease should see that manifold removed in under an hour (ha ha - famous last words, I know).

Grinding your existing manifold (or a scrap yard find - and yes, to my knowledge all large capacity K-series engines use the same manifold) is certainly the cheaper option to Mike's 4-2-1 manifold, but I am certain that the latter is the better option, and probably worth the investment. But without definitive figures... well, I guess it makes it difficult to make an informed choice.

FSE Fuel Pressure regulator:

Carl, very very interesting report there! Glad you went to all that trouble to gather such interesting data! :o) IIRC Roger Parker reckoned that 3.3 bar is the upper end of the standard fuel pressure regulator, and there maybe a simple way of modifying the existing regulator to ensure adequate fuel line pressure.

>> When I had all my mods done (except the FSE) there was a a lack of power at high speed down the long straights on the track (especially with hood down).When letting of the accelerator slightly there was a felt surge in power ! This made me assume that the engine now was running a bit lean ,at least at this specific type of driving. <<

Certainly, since the airbox mod and fitting Mike's exhaust system, I have noticed similar "symptoms" (perhaps not quite so extreme) on the road and on high-power circuits such as Castle Combe and Goodwood - so perhaps I need to check my fuel line pressure...?
Rob Bell

Hi all, yes Rob - I started the cheap way and tried to fettle with the original pressure regulator. Usually they can be either "shimmed" under the spring to bring up the pressure a bit or fitted with a hard-soldered nut and bolt for continous adjustment.Also a blow with "grandmother" (the biggest sledge at hand !)could increase the pressure slightly.
Unfortunatly it seemed that the ones fitted to the K-series does not lend themselfes to bullet proof opening and re-assembling. My fear was simply fuel leakage and possible worse scenario... So to be better safe than sorry I got my hands on a SH FSE unit and did a proper instalation. My initial pressure with the bog standard one was a bit low at 2,8 Bar and the final adjusted one very close to 3,3 Bar.
As always there is an "adjusting period" for the MEMS,at least for the VVC. A dozen starts and stops made everything very smooth indeed and the fear of holed pistons is gone!
We have been discussing this topic over here amoung both Elise and "F" drivers and there seems to be a rather big diff. between cars regarding the standard fuel pressure regulator and its value. The variations are probably due to the pressed steel type of housing and not tight enough tolerances.
Of course the state of the injectors can also play a big role here as the petrol of today can give all kind of changes to the initial spray pattern....
But that is another story !

BR, Carl.
Carl Blom

Been following this up a little Carl with Roger. Seems that there is a company in Coventry that will set up standard fuel pressure regulators for modest cost (don't ask me, I haven't got a figure yet). Easy for them to 'squeeze' the regulator until it sets the fuel pressure to 3.3bar.

Trouble is, they'll only do this to a minimum batch number, rather than a one-off. I gather that the minimum number is 10.

Anyone else interested in an OE fuel line pressure regulator that gives 3.3 bar pressure? (The acceptable limits are 2.8 - 3.2bar, so yours Carl was right at the bottom end...)

I'm in, obviously - anyone else? Need 9 more names chaps...
Rob Bell

Will this require the car to off the road for any time Rob?

Paul Nothard

Reading Rob's comments about the cat being removed, I too saw the results of testing with/without on Mpis and VVCs and, after fitting one to my VVC, have to disagree. The only mods I have done so far are the 'cat saver' and a K&N 57i filter. (See MGF General thread). Although I haven't had it on a rolling road yet, I could feel the difference. The noise thing is superficial as you can't hear the 'small' increase i exhuast noise over the filter roar! General engineering theory states that ANY kind of restriction on the intake or exhaust systems with hamper performance. But I'm open to anyone else's opinion...
Richard Stone

No it won't Paul.

Roger has warned me that the lead times can be quite long, as the jig and other equipment needs to be set up to suit - but since they'll be starting with, I guess, new fuel pressure regulators, fitting will be a simple case of removing the old and inserting the new (gosh, I make that sound easy! ;o))

I'll start the ball rolling then, and try and get a feel for prices as soon as I can.
Rob Bell

>>I have done so far are the 'cat saver' and a K&N 57i filter. (See MGF General thread). Although I haven't had it on a rolling road yet, I could feel the difference.<<

Well, effectively no gain is what we honestly saw Richard. Not that this negates your observations though. I must ask though - did you perform both modifications at the same time, or do you have any subjective evidence that the cat replacement alone made a difference?
The catalyst replacement pipe is a well trodden path, as you probably know Richard, and in fact our observation has been pretty repeatable (plenty of folks here and in "Elise world" have performed RR tests before and after installation of a cat bypass tube). Where gains were seen, no comment on the condition of the catalyst prior to removal was made (not even emissions values) - which opens the possibility that the catalyst had not been operating a optimal performance previously, and in fact was giving a higher than normal back-pressure. But unfortunately, it is not often possible to be sure if that explanation is correct or not.

As stated above, I believe that the single greatest impediment to optimal performance of the entire exhaust system is the exhaust manifold, then the back box, and then the surprisingly well designed standard catalyst. Sorting the system in that order is probably the most logical way of approaching performance modifications - but I am sure that there will be those who will disagree! :o)
Rob Bell

I think I found a gimmick at your gusto

Look for "Electronic Fuel Pressure Meter." it is mounted on the PBV and displays the pressure. How about removing the damn clock and add this there, what use is a clock anyways *g*

For some the other info ont that page might be interesting too.

Got details from the dealer, the gauge has a diameter of 52mm, that should fit pretty nicely, shoudln't it?

Yes, that should fit nicely... but how useful would it be? More useful if you could download the pressures as telemetry and then use this information to determine whether your regulator needs adjusting - which could be very usefully combined with information from an additional lambda probe as Carl described :o) ;o)
Rob Bell

Useability Level : Gimmick ;)

Talking of gimmicks - you can get digital gauges in the standard 52mm size with displays for two separate variables - oil pressure and coolant temperature, for example.

You might even get one that reads fuel pressure and lambda if you asked... ;o)

If I were getting a supercharger, then I'd be seriously tempted to get a pressure/ oil temperature combined gauge... :o) Broom broom!
Rob Bell

<<Talking of gimmicks - you can get digital gauges in the standard 52mm size with displays for two separate variables - oil pressure and coolant temperature, for example>>

wouldn't happen to have a URL would you rob? ;-)

paul weatherill

It's in the Demon Tweeks catalogue Paul (hours of endless browsing fun ;o))


(you may need to copy and paste the above)
Rob Bell

thanks Rob.

paul weatherill

Excuse my ignorance, is it possible to swap the standart analogue for a digital gauge without changing the sensor?

i guess it depends if the gauage can be calibrated, and that the signal from the sensor is within the gauge's tolerances.
paul weatherill

Good question Thierry - but at least all the gauges on the MGF are electrical as opposed to mechanical.

As Paul says, whether you can use the sender for the standard gauge with the digital items listed above depends on the reference range - but I suspect that the parts are probably industry standard??? Answers on a postcard to the usual address ;o)
Rob Bell

This thread was discussed between 12/07/2003 and 18/07/2003

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