Advice after rolling road session
Discussion
Hi,
I did kind of post this in the MG section, but I wanted a bit of more general advice regarding a disappointing rolling road session I had last Saturday.
This year, my wife insisted she wanted to keep her MGF Trophy 160 (I must stress that this is the only MG I ever rated, it was/is a limited edition Trophy racing spec car), after having HGF. I used this opportunity to fully restore the car, so that the mechanicals were as good, if not better than new. With this in mind, I first had the whole of the undersides poly-bushed, new wheel bearings all round, new brake disks, pads, braided brake hoses, new wheels and tyres.
After this, I turned my attention to the mechanicals and cooling system, replacing virtually everything – radiator, hoses, swapping out metal hoses for stainless steel, even SS jubilee clips. For the engine itself, I had a Piper 270 exhaust cam fitted, a Janspeed 4-2-1 manifold and sports cat, ITG Maxogen induction, new coil packs, Magnecor HT leads, plus, alternator, starter motor, new gaskets everywhere – a complete makeover, in fact.
For the transmission, I had a Quaife ATB helical diff, ultra lightweight flywheel (half the weight of the original) and AP racing clutch, along with new selector mechanisms (and new seals for the gearbox) fitted.
To say that it now drives and handles twice as good as before would be an understatement – it feels like a perfect package for a modestly powered small sports car – it pulls very strongly, the diff is fantastic and it handles better than new (but then, after spending so much on it thus far, I’d expect nothing less…) After all this, I had it remapped.
However, when I had it tested on a rolling road, I was slightly disappointed by the power figure - I was expecting about 175bhp (standard is 158bhp – and the engine never felt weak to start with), and the limiter for the VVC engine should have kicked in at about 7,240rpm. Also, the most disappointing figure is the loss at the flywheel, which seems almost unreal, and double the amount that is usually lost! Could this have something to do with the lightweight flywheel and diff (I have never done anything like this before, so haven’t a clue..) Do I need to take it elsewhere and a live tuning session with a rolling road?
As I said, the car feels fantastic and is much quicker than before, and the diff seems better than electronic traction control – it feels a lot better than the RR results lead me to believe.
I did kind of post this in the MG section, but I wanted a bit of more general advice regarding a disappointing rolling road session I had last Saturday.
This year, my wife insisted she wanted to keep her MGF Trophy 160 (I must stress that this is the only MG I ever rated, it was/is a limited edition Trophy racing spec car), after having HGF. I used this opportunity to fully restore the car, so that the mechanicals were as good, if not better than new. With this in mind, I first had the whole of the undersides poly-bushed, new wheel bearings all round, new brake disks, pads, braided brake hoses, new wheels and tyres.
After this, I turned my attention to the mechanicals and cooling system, replacing virtually everything – radiator, hoses, swapping out metal hoses for stainless steel, even SS jubilee clips. For the engine itself, I had a Piper 270 exhaust cam fitted, a Janspeed 4-2-1 manifold and sports cat, ITG Maxogen induction, new coil packs, Magnecor HT leads, plus, alternator, starter motor, new gaskets everywhere – a complete makeover, in fact.
For the transmission, I had a Quaife ATB helical diff, ultra lightweight flywheel (half the weight of the original) and AP racing clutch, along with new selector mechanisms (and new seals for the gearbox) fitted.
To say that it now drives and handles twice as good as before would be an understatement – it feels like a perfect package for a modestly powered small sports car – it pulls very strongly, the diff is fantastic and it handles better than new (but then, after spending so much on it thus far, I’d expect nothing less…) After all this, I had it remapped.
However, when I had it tested on a rolling road, I was slightly disappointed by the power figure - I was expecting about 175bhp (standard is 158bhp – and the engine never felt weak to start with), and the limiter for the VVC engine should have kicked in at about 7,240rpm. Also, the most disappointing figure is the loss at the flywheel, which seems almost unreal, and double the amount that is usually lost! Could this have something to do with the lightweight flywheel and diff (I have never done anything like this before, so haven’t a clue..) Do I need to take it elsewhere and a live tuning session with a rolling road?
As I said, the car feels fantastic and is much quicker than before, and the diff seems better than electronic traction control – it feels a lot better than the RR results lead me to believe.
Your arse dyno is telling you the car is hugely better in every respect, this is a much better indicator than some numbers scribbled down by a rolling road operator. Rolling roads are horribly inaccurate unless the operator is very well clued up on making adjustments for air temp and doign a proper run down reading to calculate trans losses. Even then it's not that accurate.
I would get it remapped as it's probably not making best use of the new cam with the standard mapping but don't get hung up on RR figures, they're only real purpose is for pub bragging. What it feels like in the seat of your pants is all that matters.
Nick
I would get it remapped as it's probably not making best use of the new cam with the standard mapping but don't get hung up on RR figures, they're only real purpose is for pub bragging. What it feels like in the seat of your pants is all that matters.
Nick
Leptons said:
You have reduced rotating mass and therefore Torque. The flywheel loss figure is calculated by letting the wheels coast to a halt. Obviously you are going to have a higher loss now because of this.
Ahh, thank you for that - so the loss is calculated as it powers down, not up? I guess that would explain why the flywheel, which weighs less than half of the original would show double the loss...HorneyMX5 said:
Your arse dyno is telling you the car is hugely better in every respect, this is a much better indicator than some numbers scribbled down by a rolling road operator. Rolling roads are horribly inaccurate unless the operator is very well clued up on making adjustments for air temp and doign a proper run down reading to calculate trans losses. Even then it's not that accurate.
I would get it remapped as it's probably not making best use of the new cam with the standard mapping but don't get hung up on RR figures, they're only real purpose is for pub bragging. What it feels like in the seat of your pants is all that matters.
Nick
You are right, and I think it needs another remap/tuning session to get the best out of the upgrades.I would get it remapped as it's probably not making best use of the new cam with the standard mapping but don't get hung up on RR figures, they're only real purpose is for pub bragging. What it feels like in the seat of your pants is all that matters.
Nick
Oh yes, I also had a new quicker steering rack and bulstein dampers fitted. I am sure it is now as quick (or, at least feels as quick) in the twisties (40-60) as the Tamora - this is the car's natural habitat, and is what I wanted it upgraded for.
Chicane-UK said:
Worth getting it remapped perhaps to take into consideration all the modifications that have been made, especially the cam?
What fuel did you run it on for the RR session? Was it the same tank of fuel that had been in the car prior to it coming off the road?
It had a 'generic' remap after the new parts were fitted, I don't think this was a good idea, I should have waited for live tuning session I think. The car has standard 95RON (It is now so good on fuel, we haven't had to fill it yet, after the new parts were fitted) - but I was told that higher octane would be better, as the original remap makes better use of this.What fuel did you run it on for the RR session? Was it the same tank of fuel that had been in the car prior to it coming off the road?
What ECU are you runnig? the standard one? with the standard map? In which case I'd expect you'd be seeing very similar power to before all the changes. You need a new map in the ECU (which might mean a new ECU) so the engine is fueled correctly to make the most of your new set up.
To compare... I have similar engine in my caterham. vvc trophy, with solid 285 cams, roller barrel induction system and custom 4-2-1 exhaust. I'm getting around 190bhp.
As for the fly wheel weight increasing the power train losses... that doesn't sound right. The wheels will slow down quicker as there is less mass in the system, but that doesn't mean more losses. The rolling road should be measuring the resistance to slowing down to work out the losses.
To compare... I have similar engine in my caterham. vvc trophy, with solid 285 cams, roller barrel induction system and custom 4-2-1 exhaust. I'm getting around 190bhp.
As for the fly wheel weight increasing the power train losses... that doesn't sound right. The wheels will slow down quicker as there is less mass in the system, but that doesn't mean more losses. The rolling road should be measuring the resistance to slowing down to work out the losses.
c7xlg said:
What ECU are you runnig? the standard one? with the standard map? In which case I'd expect you'd be seeing very similar power to before all the changes. You need a new map in the ECU (which might mean a new ECU) so the engine is fueled correctly to make the most of your new set up.
To compare... I have similar engine in my caterham. vvc trophy, with solid 285 cams, roller barrel induction system and custom 4-2-1 exhaust. I'm getting around 190bhp.
As for the fly wheel weight increasing the power train losses... that doesn't sound right. The wheels will slow down quicker as there is less mass in the system, but that doesn't mean more losses. The rolling road should be measuring the resistance to slowing down to work out the losses.
Hi, cheers, the ECU is MEMS 3, and was remapped by Z&F Tuning (the guy who mapped the original MEMS 3 engines)To compare... I have similar engine in my caterham. vvc trophy, with solid 285 cams, roller barrel induction system and custom 4-2-1 exhaust. I'm getting around 190bhp.
As for the fly wheel weight increasing the power train losses... that doesn't sound right. The wheels will slow down quicker as there is less mass in the system, but that doesn't mean more losses. The rolling road should be measuring the resistance to slowing down to work out the losses.
I did think about blanking off the VVC mechanisms and using the solid cams, along with stronger pistons and con rods and Jenvey throttle bodies - but I wanted to give not just the engine, but the whole of the internals a complete makeover. I figured about 175/180bhp would suit the car perfectly, which is what I was aiming for.
chris watton said:
Ahh, thank you for that - so the loss is calculated as it powers down, not up? I guess that would explain why the flywheel, which weighs less than half of the original would show double the loss...
Er.. coastdown losses measure power lost through the transmission, wheels, tyres etc. with the car out of gear - ie. disengaged from the engine. The weight of your flywheel will have nothing to do with that at all. 50 brake losses seems massively high, 20 - 25 should be more like it.
chris watton said:
It had a 'generic' remap after the new parts were fitted.
This is part of the problem a generic map is a waste of time on a std car let alone a modified one, take it to dyno & have mapped properly where they can monitor afr/knock/timing etc & make adjustment to get the best out of your engine.Don't worry too much about the numbers they are great for pub/forums but who cares about that when your driving it!
danwebster said:
chris watton said:
Ahh, thank you for that - so the loss is calculated as it powers down, not up? I guess that would explain why the flywheel, which weighs less than half of the original would show double the loss...
Er.. coastdown losses measure power lost through the transmission, wheels, tyres etc. with the car out of gear - ie. disengaged from the engine. The weight of your flywheel will have nothing to do with that at all. 50 brake losses seems massively high, 20 - 25 should be more like it.
Rolling roads are useful for back to back comparisons, all other factors being equal and for live mapping of an ECU, but I wouldn't set too much store by a single run.
t anyway! 
Guys,
Thank you, I really appreciate the input. I admit that I was very apprehensive about starting this post, with it being an MG and probably worth very little to most – I thought I’d get much abuse!
I wasn’t/ am not interested in pub figures, I just wanted to have a better knowledge as to why the figures were not as good as I anticipated, the loss at the flywheel being the main concern – which is totally at odds with the way the car now accelerates, compared to before. I do not for one minute pretend that it’s some kind of drag racer (it’s a 1.8…), but I do want it to be as good as it can be when having fun on the B roads – and be robust enough to last at least another 10 years (it has only got 50K miles on the clock for an 11 year old car)
I think the best upgrade was the Quaife diff, and I’d recommend it for those who have MX5’s, MG’s Lotus’s – it was so much fun even in the downpour we had last Saturday.
So, what it needs is a live tuning session, and fill the tank with higher octane fuel beforehand?
Thank you, I really appreciate the input. I admit that I was very apprehensive about starting this post, with it being an MG and probably worth very little to most – I thought I’d get much abuse!
I wasn’t/ am not interested in pub figures, I just wanted to have a better knowledge as to why the figures were not as good as I anticipated, the loss at the flywheel being the main concern – which is totally at odds with the way the car now accelerates, compared to before. I do not for one minute pretend that it’s some kind of drag racer (it’s a 1.8…), but I do want it to be as good as it can be when having fun on the B roads – and be robust enough to last at least another 10 years (it has only got 50K miles on the clock for an 11 year old car)
I think the best upgrade was the Quaife diff, and I’d recommend it for those who have MX5’s, MG’s Lotus’s – it was so much fun even in the downpour we had last Saturday.
So, what it needs is a live tuning session, and fill the tank with higher octane fuel beforehand?
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