The Rollers of Truth

[Guest]

You lads had a good day at the Dyno.. the chat is only just tailing off...! Unfortunately due to our remote location in Co.Galway we couldnt make it so today we headed up to Enfield , Co.Meath to a place called Westward Precision Engineering. It was a nice chap called Martin Tracey who done a rolling road session with Thomas's beloved Faye. The reason being was 1. We wanted to see how Faye was performing before we undertake a few mods. 2. Most importantly a day out for the boys[]

As you all know Faye is an '87 Turbo with 147k miles on. The only mods carried out on her are a K26/8 turbo, a Lyndsey hard pipe kit and a horrible cone air filter which is behind the bonnet catch (to catch as much hot air as possible off the IC [:'(])

Faye waits her turn

Martin runs Faye to max power.

Faye went very well indeed with 219.5bhp at the flywheel at 6125rpm and 299nm of torque. Not many horses escaped even though she has a bit of a leaky exhaust.

Heres the important bit[]

Martin then took us aside and explained what all the curves meant in laymans terms. Every day is a school day and I learned a bit today...!

Can any of you lads see anything strange in these graphs.... ?
Does the turbo really pulse like that?

 

[Diver944]

Looks about right for an early car to me. I would have hoped the K26/8 turbo would have given you a bit more but if everything else is standard, it's not letting you use the extra boost it is capable of.

If I read the pink line correctly it looks like it is hitting just over 0.7 bar of boost by 3500rpm, then tails off to 0.6bar at 5000rpm which it holds to the redline. A simple chip or remap and an increase in boost to 1bar should see a healthy rise. A better wastegate will bring the peak boost on about 500rpm earlier. Shame the dyno did not record the AFR but not all of them do that

 

[bigkeeko]

Good on you for sticking her on the rollers. Rolling road days are a laugh and theres always some surprised looks and excuses.

I bet if some of the older Lux`s were strapped down there would be some red faces at the end of it. []

 

[Guest]

It was good owl craic alrite.. really enjoyed it... We had a chat with Martin and he said that it was no problem having a dyno day at his place. We will get a few organised for it next year...!

As for Faye - the modifying bug has well and truly got hold now... Thomas plans to get a few bits like a proper hotwire AFM, DP wastegate, piggy back ECU and manual boost controller.... along with a new exhaust...! Faye is out of tax in November so she is going in over the winter months and Thomas is going to abuse his credit card....! []

As for my car.... I intend keeping her standard ..its very difficult as I have been bitten very badly by the tuning bug now ... but at least I have Faye to play and experiment with .....!

 

[rd944]

ORIGINAL: bigkeeko
I bet if some of the older Lux`s were strapped down there would be some red faces at the end of it. []

what do you reckon they'd show at the wheels ? 120bhp ?

 

[wjk_glynn]

Its like the old saying... there's lies, damn lies and dyno numbers []

Speaking of which, when it comes to dyno numbers, I've noticed a difference in how values reported in the US and in the UK. Here in the US, the number quoted is usually the rear-wheel number (with SAE corrections and so on) because quoting the crank number requires an accurate estimate of the drivetrain loss (and coming up with that estimate often degenerates into 'religious' wars). But when I see dyno numbers quoted in the UK (or Ireland), it's nearly always a crank number -- with the implication that the dyno equipment can accurately measure the drivetrain loss as things coast down.

My rule-of-thumb drivetrain loss number for the 944/951/968 is 15% (treat that as a rough approximation). That's based on looking at a lot of rearwheel dyno numbers for 'stock' cars and seeing how they kinda average out.

If I'm reading Donal's data sheet correctly, it seems to say the car is making about 160-hp at the wheels, and then its estimating the crank output at 220-hp. That's a 27% loss, which seems awfully high (IMO).

I've no idea what it means... just an observation.

Karl.

 

[wjk_glynn]

ORIGINAL: VanhireBoys
...due to our remote location in Co.Galway...

I'll be in Galway myself over the Christmas, hopefully enjoying a few scoups in Murphy's on High St []

Karl.

 

[rd944]

FWIW 240bhp TVR's tend to show about 160bhp at the wheels, given that TVR's figures have always been optimistic and a true crank figure is probably 220, this would correlate well with the drivetrain losses seen here.

given the same losses that puts a lux @ 115ish and a 924 @ 90 !

 

[bigkeeko]

ORIGINAL: rd944

ORIGINAL: bigkeeko
I bet if some of the older Lux`s were strapped down there would be some red faces at the end of it. []

what do you reckon they'd show at the wheels ? 120bhp ?

. Of the few 2.5 944s I`ve driven I can`t say any of them were particularly fast I`d say 120bhp is optimistic.

 

[Guest]

ORIGINAL: wjk_glynn

I'll be in Galway myself over the Christmas, hopefully enjoying a few scoups in Murphy's on High St []

Karl.

Give me a PM closer to the time and we can get scuttered and chat c**p []

If you are bored you can watch Faye getting dynoed on Youtube. Its me shaking my head and telling Thomas why the ABS light is on. It only gets going at about 4:36[]

http://www.youtube.com/watch?v=2KG5m-ekig4

 

[barks944]

My 1984 2.5 8v hit 102 bhp at the wheels.

 

[Fen]

I think 15% is about right for the transmission losses on a 944 as well, Glynn. That is based mostly on the figures we used to see at Weltmeister.

I tend to agree that wheel power is a better figure to use as you are avoiding a back-calculation using an estimate of transmission losses and it relates more directly car to car, but I also have to say that a lot of the RWHP figures I've seen posted on Rennlist are a tad optimistic to my eye.

 

[barks944]

My 944 8v was 150bhp at the crank and 102 at the wheels. Thats a 33% loss.

 

[wjk_glynn]

ORIGINAL: barks944

My 944 8v was 150bhp at the crank and 102 at the wheels. Thats a 33% loss.

Hi Tom,

Did you do both an engine-dyno and rear-wheel-dyno test to get both of those numbers? Or was it just a rear-wheel-dyno measurement, with a derived crank estimate?

Thanks.

Karl.

 

[wjk_glynn]

ORIGINAL: Fen

I think 15% is about right for the transmission losses on a 944 as well, Glynn. That is based mostly on the figures we used to see at Weltmeister.

I tend to agree that wheel power is a better figure to use as you are avoiding a back-calculation using an estimate of transmission losses and it relates more directly car to car, but I also have to say that a lot of the RWHP figures I've seen posted on Rennlist are a tad optimistic to my eye.

Another factor is the variability (or lack or repeatability).

There are lots of Dynos out there: http://www.weissach.net/Suppliers_Dynamometers.html. Here in the US, the Dynojet is well respected.

A couple of years back, Turbo Magazine took a stock 350Z around to six different dynos in single day: http://www.turbomagazine.com/tech/0306tur_turbo_magazine_dyno_dash/index.html

They got the following rear wheel numbers:

Dynapack 249.4
DTS 257.6
Dynojet (Win) 235.8
Dynojet (DOS) 243.7
Clayton 265.7
Super Flow 228.9

As you can see, they're all over the place. Now a 350Z back then made 287-bhp (SAE). Applying a 15% rule-of-thumb loss (for the sake of argument), you get 244-bhp. The Dynojet is closest.

In another article, Car and Driver wrote about the effects of temperature on Dyno results: http://www.caranddriver.com/reviews/hot_lists/high_performance/features_classic_cars/is_your_dyno_lying_tech_stuff

Lots of grist for the mill...

Karl.

 

[barks944]

that was a test of rwhp with derived crank hp. i think my car is supposed to be 150 so it seems accurate. theres a link to the dyno chart in my 8v engine tuning thtead.