MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Rolling Roading at Peter Burgess Again!

I spent yesterday morning at Peter Burgesses place, hanging out trying to sound intelligent when talking about cars and engines and doing some tuning work on my 1500 EFI.

It's my fifth visit and fourth go on the rollers. It's always a pleasure and an education, the car wouldn't be half as good as it is without him. There is no BS, no sales pitches, just a straight up vast wealth of information based on decades of testing and scientific experimentation. A true enthusiast of his craft and all round top bloke!

So the headline figures are now 105.63hp @ 5400 and 116 lb-ft @ 3400 (both est. flywheel). Compared to 2022, there has been a top end gain of 13hp and about +12-15% throughout the rev range. All from fitting Peters big valve, high compression head this winter.

It makes the car pretty punchy and I did almost smear it sideways into a hedge when I thought "let's see what it will do pulling out of this junction". Oops - idiot! ha ha!

The graph shows the iterations I have been through over the years from a DCOE on a dodgey manifold that wouldn't flow when you gave it full throttle (!), to fancy (albeit totally OTT!) setup I have now.

Thanks again Peter! We will get it to 110... already pondering a new manifold... ;-)

Cheers,
Malc.






Malcolm

Malcolm,

Did you see the dual plenum and CFD analysis page that William posted? Food for thought.
David Billington


Very very nice.

Was there any discussion about it 'needing' a hotter cam?

Bet you could have it making power to at least 6k :-)

(Although of course that torque at 3400 is most impressive)

Mr B's engine built for me was doing so 20+ years ago, although not reaching the power yours is producing much lower down, but it was on a pair of SU's.

Pretty punchy? I do like a bit of understatement.
K

Yes, I did see the CFD thing David, thanks. No more mods for now. Time to drive it, enjoy it and I can do some research and design and decide if I want to go another step.

K, stuck with the 285 cam as everything else in the engine had been designed to match with it. We did take it up to 6k, so it will happily spin that fast, but it's not making any power that high.
Malcolm

Good stuff Malcolm
I'll a bit envious
I'd love to be able to say "I spent yesterday morning at Peter Burgesses place,"
William Revit

You would have been very welcome - and actually your name came up in conversation Willy ;-)

Don't worry, it was in a good context, along the lines of "that Willy bloke has done some fun and really smart stuff with engines".

Malc.
Malcolm

You would have been most welcome Willy. I would have liked to have been able to say I have met you too!
Peter Burgess Tuning

Cheers
William Revit

OK... so I have had chance to ponder this over the week, and this isn't over! ha ha ha!

Plotting the torque curves from 2022 (red) vs 2023 (green), when the new head was installed.

Plotting an additional theoretical curve, blue, which is the 2022 curve but transposed up the axis by 17 lb-ft so that it matches red at the mid range, it shows how badly the current setup (green) performs over 4000 rpm. That should be where the fancy head work should be coming into it's own I would have thought.

I'm with you Peter, we should be seeing more up high and I think the inlet manifold needs a proper re-think about and re-do. I'm not happy that it is flowing right and adequately supplying all four cylinders.

There is 110hp in there for sure!

Malc.



Malcolm

"and this isn't over! ha ha ha! "

Did you really think it would be--------------

It is a bit strange that both power and torque drop off together at that 5 1/2 ish spot----you would sort of expect the torque to be dropping off but HP - you'd think would drop off more gradual and not that early with the cam you've got-

Could be running out of fuel--
I'd reckon your actual fuel supply is ok, but a gauge in the line and a squirt up the road will tell the story there.
Does your pcm have a rev limiter built in--I forget what brand you have, but
Some pcm's have choices for rev limiting as in hard cut or soft cut----If yours is set up as soft cut at for example 6000rpm it'll start fuel cutting and timing reduction possibly 500rpm earlier and cause a drop like you have there
If it is a soft cut i'd be tempted to poke it up to something like 7000 so it starts working around 6500 instead-----that'll still be low enough to save your engine if you miss a gear etc
The other possible is that your muffler isn't flowing enough but that's usually when you run a baffle type muffler---i suspect yours might be more sporty flow through type--? so probably not an issue
William Revit

Thanks for the ideas Willy.

We had the same thought on the rev limiter and bumped it up on the later runs with no change.

fuel pump should be able to pump enough - it's 150 L/min or something like that and 8mm hose. Injectors are getting reasonably high on the duty cycle (80s %) but should be OK and the AFRs were coming out OK, not leaning off.

Yep, exhaust has straight through silencers.

The thing I forgot to mention was that we cranked in 34 degrees advance, whereas previously it was happy with 30. Would this suggest poor cylinder filling, i.e. crap air flow?

Cheers,
Malc.
Malcolm

The drop off looks too sudden for inlet airflow, that usually shows up as more of a gradual strangle/curve-
Fuel starvation is a strange dude to diagnose sometimes
The AFR can still show correct still right up to when it hits the wall. 80% duty is still ok---what % have you got at idle speed
First off I'd be tempted to hook a gauge in as close to the injector rail as possible and go for a thrash just to make sure there's not a supply issue at high revs/load
William Revit

Okie dokie, will look into it. Thanks Willy, you are a legend! :-)
Malcolm

just a thought
When you were filling in your fuel map, have you filled in values in all the boxes after 6000rpm up to 7000 +
Not sure if your pcm is similar or not but the motec pcm's that are popular here have to have values in all the boxes even after the rev limit otherwise, if they're not filled in the pcm will sort of blend the value from the last filled box down to 0 if the next box isn't filled with a value.
Same with ign timing if that's going through the pcm.
hope i've explained that enough
William Revit

Hi Willy, no messing this weekend, just out and about driving! MASC 40th anniversary gathering at the British Motor Museum here in Blighty.

Re: the mapping thing. The maps are only setup/populated up to 6000rpm. But I am certain I read somewhere that if the ECU finds itself outside the map, it uses the last known value on the map. i.e. if it says 100 on the fuel map at 6000, it will assume 100 all the way up to infinite rpm.

Out of interest, what does PCM stand for? I understand what you mean, just never come across that acronym before.

Cheers,
Malc.



Malcolm

Passing by all the cars at Gaydon yesterday, I came across an unoccupied orange beast that could only have belonged to Malcolm.

It’s an impressive looking engine arrangement, barely contained within the engine bay, lovely looking thing.

I didn’t get to meet you Malcolm, but I did see you at a distance.

Respect.
Philip Sellen

sorry malc. yeah my bad.
ECU and PCM
ecu -engine control unit
pcm -powertrain control module
i tend to call them pcm's as a lot of them here have the auto trans unit built into them, so it's more of a power train controller than just engine control.
either,or, same thing

On the mapping-yep, I've heard that some units do that but if you're on top of being able to enter some values which I'd imagine you are, I'd be tempted to fill some boxes in through to 7000+ just to see if it makes a difference--you never know how the box is thinking, it "might" be acting like a rev limiter just because the boxes aren't filled----just use the 6000rpm values you have and extend them accross
William Revit

Thanks Phil. Really appreciate your kind comments.
I'm sure our paths will cross at some point :-)
Malcolm

My two penn'orth; the plenum and runners may be able to be improved volume wise and shape and runner length wise. I also think plastic plenum chamber and runners would greatly assist with running at a far cooler temp than the stainless one. 3 degrees C = 1% more bhp.
When folk do a before and after and back again test removing some of an intake system to fit K&Ns on a modern efi engine I have never seen an improvement over the standard fitment fully tuned/developed by the factory package.
Malc has taken on quite a task developing an efi on a single throttle body and not on separate throttle bodies.
It would be interesting if Malc could borrow a pair sideraft Webers set up to try on and see what bhp could be achieved and have a 'target'. Difficult in practice with high pressure fuel supply I suppose?
Peter Burgess Tuning

Cheers Peter
To be honest it looks fine like it is--my input was more or less just trying to think of little weirdies that might be lurking
The only thing that looked a bit strange was how the HP dropped suddenly at that 5500rpm spot on Malc's drawn graph but that might not be an issue at all as it could be exactly what happened on the rollers if it was run up to 5500 and then backed off---it could well still be strong at 6000 if that's the case

willy

William Revit

Please some more photo's of Masc 40
A de Best

Hi Willy, I stopped pushing for higher revs as the engine 'didn't want to go there'
Shame we haven't got a few million between us all to develop it!
Malc has done a stunning job on this to his great credit.
Peter Burgess Tuning

Been messing in CAD... during my lunch breaks and after hours of course *cough*

I can't feasibly package the "rule of thumb" 18 inch long runners for optimal pulse tuning. But can get in half that length and try to capture a secondary harmonic. 9 inches, minus the 3 inches in the port = six inch runners. Up from the 4.5 inch currently (which are only that length because my mate that made them cut them too short!!).

Plenum upped from 60 x 60mm square cross section (3600 mm2) to a 3" nominal pipe (approx 4200mm2), an increase of approx 16% cross sectional area/volume. And extended beyond no. 4 cylinder to gave that cylinder a bit more breathing room.

Pondering what to do at the runner entrances. The rad I can get on them is so small (1/4") the theory suggests a chamfered inlet would be give or take just as effective. But a rad does just seem correct.

Make it out of aluminium this time, not stainless steel. If nothing else, it saves a kg!

That's this winter sorted... ha ha :-)






Malcolm

That looks good Malc. Do you think any pulses may be reflected from the closed end of the plenum and maybe cause problems at any rpms? Could a different shape kill off reflected waves, sort of stealth fighter technology?
On a lighter note, for which I apologise, can anyone remember Graham Greene's novel 'Our Man In Havana'?
Peter Burgess Tuning

Alec Guinness as the vacuum cleaner salesman who is an unofficial spy!
Bob Beaumont

Malcolm
Been thinking about your car- there can't be much wrong witth it really
Where your exh. joins at the collector, what diameter is the collector and how long is it untill it reduces to exhaust system size---also what size is your system as in o.d. of pipe size through the muffler(s) and out the back----
I'm thinking if the system is restrictive it might be limiting scavaging while both valves are open, your inlet manifold could be good but fighting the exhaust ------------maybe
William Revit

This thread was discussed between 16/05/2023 and 27/05/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.