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Life after Westy's...earning my petrolhead stripes

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Archibald Meatpants

Nice result. What’s the estimated flywheel figure and how much boooooost?

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BCF
1 hour ago, Archibald Meatpants said:

Nice result. What’s the estimated flywheel figure and how much boooooost?

 

Have a closer look at the photo...

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AdamR

Hmm. Something not right with the numbers there.

 

Though if it drives right and you enjoy it, who cares, great result! Chuffed for you dude.

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Archibald Meatpants
29 minutes ago, BCF said:

 

Have a closer look at the photo...

 

Cant see what I’m supposed to be looking at but nice result 

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BCF
19 minutes ago, AdamR said:

Hmm. Something not right with the numbers there.

 

Though if it drives right and you enjoy it, who cares, great result! Chuffed for you dude.

 

What do you mean buddy?

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BCF
5 minutes ago, Archibald Meatpants said:

 

Cant see what I’m supposed to be looking at but nice result 

 

It shows 203bhp as the fly figure, no boost though (sorry, ignored that bit before). Its making about 6-7psi. More to come with a replacement actuator :yes:

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AdamR

203 at fly and 189 at wheels don't really correspond... normally losses are quoted at 20% ish.

 

With 7 psi / half a bar of boost I think you're normally more like 1.5x the original power? With a proper ECU I think these engines make about 130-140 at the fly so it's on the money with 200, just 190 at the hubs seems high.

 

Anyway I'm just blurting out thoughts, feel free to ignore me, it's how it drives that matters!

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BCF

Well, Neil did explain all this to me, so I'll do my best to regurgitate that information...

 

It's a single roller dyno, so the losses are much less than a twin roller. It was calculated using a coast down test (I think that's what it's called) which provided an 'accurate' view on the losses, so is much less than you'd expect. He was very scathing when I asked him about the 15-20% losses rule, as he said that doesn't work in real life - for example, an mx5 making 200bhp at the wheels and therefore theoretically 240bhp at 20% loss has the same mechanical components creating the loss if it made 400bhp, but would not equate to 480bhp - the mechanical loss is the same, not extrapolated. 

 

Either way, I know BRG is 189bhp at the wheels and I'm well happy with that!

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maurici

With all do respect, that guy as many many other dyno users, have it wrong. Stills suprises me that proffesionals of the matter cant understand the tools they are using (and even with that they sometimes deliver good results anyway).

 

Loses, are basically lacks of efficiency of the machine (machine in this case the drive/power train of the car), and is given with a coefficient.

This coefficient, is effectively a percentage.

In the car, you have to beat the static friction of the components (negligible, you can start the movement by simply pushing it with your legs... maybe half hp) and then the dynamic friction of the components and gears spinning in a bath of oil. As more movement you have, and the faster you try to move it or change the speed the greater the dynamic friction will be, the less efficient the machine will be, and the loses will be MUCH greater.

 

A 400hp mx5 will try to move the bits and change the speed on them ( accelerate ) much faster than a 200hp mx5. Therefore you should expect greater loses. (And you will have them). That is why the only relevant bit is the wheel HP, and the flywheel hp is pure bul****, and nobode have a clue of what they are calculating.

 

Sorry, the explanation doesn't looks very clear... I've done my best.

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BCF
11 minutes ago, maurici said:

With all do respect, that guy as many many other dyno users, have it wrong. Stills suprises me that proffesionals of the matter cant understand the tools they are using (and even with that they sometimes deliver good results anyway).

 

Loses, are basically lacks of efficiency of the machine (machine in this case the drive/power train of the car), and is given with a coefficient.

This coefficient, is effectively a percentage.

In the car, you have to beat the static friction of the components (negligible, you can start the movement by simply pushing it with your legs... maybe half hp) and then the dynamic friction of the components and gears spinning in a bath of oil. As more movement you have, and the faster you try to move it or change the speed the greater the dynamic friction will be, the less efficient the machine will be, and the loses will be MUCH greater.

 

A 400hp mx5 will try to move the bits and change the speed on them ( accelerate ) much faster than a 200hp mx5. Therefore you should expect greater loses. (And you will have them). That is why the only relevant bit is the wheel HP, and the flywheel hp is pure bul****, and nobode have a clue of what they are calculating.

 

Sorry, the explanation doesn't looks very clear... I've done my best.

Lol, no, makes perfect sense dude, basically exactly what Neil said! Just my bad translation. The point is, don't just apply a 20% threshold, work it out through a coast down so its accurate for that car, which is what he did :yes:

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BCF

I have now moved this thread over to another forum:

 

https://www.pistonheads.com/gassing/topic.asp?h=0&f=47&t=1817335

 

I really appreciate those that have engaged and commented so far, it's been fun! However keeping one thread up to date is all I can handle, so doesn't make sense to keep this one going when I recognise this isn't really the right place for it. See you on the other side!

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Dave (OnliestSmeg) -  Manchester AO

Shame you've moved this @BCF as have been following with interest - it's turning into an MX5 I need! 😁

Totally understand though, not wanting to update 2 threads.  I'll try keep up on pistonheads.

Good work!!👍👍🏻

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BCF

Ha ha, thanks Dave, appreciate it. They've sort of taken slightly different turns, and as more people seem to engage with the pistonheads thread, it makes sense to focus on that. 

 

Update on it's way!

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