JHM's SC

[FaisalJ]

I feel like I've logged into audizine! They're obsessed with how quickly they can go in a perfectly straight line over a short distance, and get very upset about it all. Bless em.

I don't think they have enough bends over there!

Joking aside, this would seem to be pretty good value. I also find it odd JHM don't have a UK agent? Surely there would be enough of a market for their products over here to make it worthwhile. Anyone know more?

[RossDagley]

Is it me or is that drag strip down hill??

[PetrolDave]

I feel like I've logged into audizine! They're obsessed with how quickly they can go in a perfectly straight line over a short distance, and get very upset about it all. Bless em.

I don't think they have enough bends over there!

I remember having an onging "debate" over several years on here with a (now banned) member called with sakimano that straight line speed only proved that a car had good power and traction but said absolutely nothing about handling and drivability - a point he absolutely couldn't see, even when I illustrated it with an example where a Renault 5GT Turbo was faster over a given stretch of rural Norfolk road than a Lotus Esprit despite having less than half the power and being driven by a worse driver (me vs. an ex-F1 driver).

[iduff]

I think sakimano now makes the point that ¼ mile times are a more fair estimate of power than various dyno outputs. There's no fooling the time and trap speeds, whereas various dynos will report different numbers for the same car. Coast-down driveline loss estimating, power measurement mechanism, all sorts of variables that can lead to different outputs for the same input/car.

There's no question we do not own dragsters, but a drag strip is a great way to compare engine output.

I'm hesitant to go to a drag strip with my new to me RS4, since I don't want to fry my OEM clutch, nor risk blowing up an 80K miles engine whose maintenance I only took over a few months ago when I bought it. Straight-line acceleration is the best way to easily baseline and track performance and mods, so I'm doing the poor man's drag strip, i.e. 3K-8K 3rd gear pulls.

sakimano has provided good insight into this for me, and I think may have grown to appreciate that we have sports sedans, not dragsters. Either that, or he always appreciated it and his message was blurred when you were "debating".

There's lots of objective information on superchargers, and JHM is part of that, out there. JHM generally gets good reports.

It's interesting to me to find JHM, and the attention they pay to our B7 RS4, particularly coming from my C4 S6 background, where JHM is virtually unknown. I'm happy to have found them, happy to have made an online acquaintance with sakimano, and happy to have found this forum.

[PetrolDave]

¼ mile times are a more fair estimate of power than various dyno outputs.

There's no question we do not own dragsters, but a drag strip is a great way to compare engine output.

100% agree that dyno outputs are useless in absolute terms and should only be used for before:after or car1:car2 comparison testing.

1/4 mile times are not just a measure of engine power output as they can be greatly affected by the skill (and reaction time) of the driver and the grip of the tyres - the poor 1/4 mile times of the twin-turbo RS4 posted here and on audizine are attributed by the owner to his lack of driving skill and possibly also to his poor tyre choice.

If there is an excess of power over handling what you get is a car that is useless as a daily drive, for example a top fuel funny car with maybe 8,000bhp at the top end of its rev range has amazing 1/4 mile times but has such peaky power & torque characteristics that its of no use whatsoever on normal roads, especially European roads with lots of bends and elevation changes where drivability is at least as important as peak power.

These factors are why I have always maintained that the lap time on a challenging road course (Road America, Brands Hatch,Nordschleife, ...) is a better measure of the usable power/torque of a car intended for road use than either 1/4 mile times or dyno plots.

[iduff]

Makes sense

[denis.dasilva2]

[RossDagley]

Is it me or is that drag strip down hill??

Every strip/track 1/4 mile,its made like that, an straight line and then up hill so it can help slowdown the cars,thats why you have an impression that is downhill!

Er... No! Not true.

Notwithstanding that, it looks downhill before the uphill part - and I don't believe it's an optical illusion. Which drag strip is it?

[denis.dasilva2]

[RossDagley]

Sacramento raceway! Everything here on this forum is starting to sound like AZ! Im out !

Don't get butthurt.

Whilst I appreciate the Americans might need a downhill section to get decent quarter mile times, that's just not how we do it here in the uk.

[esp_mm-270]

Yeah, this site (read members) is so <beep> now. Gobby tossers. Call to PhilT, please delete my user ac from this site.

[esp_mm-270]

Bleep = S h i t

[JCviggen]

Whilst I appreciate the Americans might need a downhill section to get decent quarter mile times, that's just not how we do it here in the uk.

Nice going making this site look like it's full of twats. That last little bit of uphill at Santa Pod doesn't influence times nearly as much as you'd think. I calculated it once, without remembering the exact percentage it was definitely pretty small and it's also worth noting that the first bit of the Pod (where it would influence traction) isn't uphill but rather the opposite (making the second part look even steeper than it is)

And he's right about that US strip, it IS level for all intents and porposes. And there are quite a few strips that are uphill after the finish line, the one he posted is not downhill.

On the whole, things like altitude and ambient temperature will make a bigger difference to the actual results than a not-quite-perfectly-level strip anyway. That's my main problem with comparing performance numbers in general, when done in different places in different temperatures they just aren't comparable.

On JHM in general, I'll say one thing: It's nice to get awesome results without being forced to go out of your way to get your car "custom" mapped somewhere. Their tune just works without unnecessary inconvenience and expense from the moment you flash it into your car from your own driveway.

[RossDagley]

Nice going making this site look like it's full of twats.

Speak for yourself. It was meant tongue in cheek

That last little bit of uphill at Santa Pod doesn't influence times nearly as much as you'd think. I calculated it once, without remembering the exact percentage it was definitely pretty small and it's also worth noting that the first bit of the Pod (where it would influence traction) isn't uphill but rather the opposite (making the second part look even steeper than it is)

I didn't say it did. I'm demonstrating that SP doesn't have an uphill section at the end despite the previous post "Every strip/track 1/4 mile,its made like that, an straight line and then up hill so it can help slowdown the cars". SP actually has a 2m elevation change across it's measured 1/4 length - uphill. For all the difference that makes...

Edit to add: having now checked, I can see it IS in fact an optical illusion (caused by the end uphill section) - Sacramento raceway is 32m MSL across it's measured length, then goes up hill

On the whole, things like altitude and ambient temperature will make a bigger difference to the actual results than a not-quite-perfectly-level strip anyway. That's my main problem with comparing performance numbers in general, when done in different places in different temperatures they just aren't comparable.

I completely agree. Perhaps that's why American dynos generally read 10-20% higher than UK dynos... Oh wait... another can of worms

[JCviggen]

I think the dyno thing goes back to Americans being used to "wheel" horsepower which isn't really wheel horsepower. Europeans are used to crank horsepower which isn't really crank horsepower.

Each side uses a type of dyno that suits the local perception best.