Dyno'ing an SC Monaro
Discussion
Right, after huge amounts of time and effort from lots of people we now have some difinitive details on how and what and (interestingly) another set of data to assimilate.
As most people here know Chris (BO55) has had some work done on his car and he came to us (Thorney Motorsport) to do some measuring. The numbers that came out were not as high as he was expecting and (via some fairly unpleasant name calling, not by Chris I add) it came to the result that further testing at another dyno was needed to put the matter to rest.
Chris went to WRC in Silverstone where further runs were done (paid for by Vauxhall, which was nice of them) and the numbers were (I believe, I've not seen the charts) were circa 400bhp (401 I think). Seeing as at TMS we 'only' saw 358bhp (at the wheels) I asked Chris to come back so we could run the car again if there was any discrepancy (which obviously there was).
In between this time I contacted Dyno Dynamics to get their official stance on how to power measure SC Monaros (seeing as Dyno Dynamics are Australian I took the view they know what they're doing) and their instructions were thus:
1. Run the car in 3rd gear
2. Inflate the tyres to 50psi
3. Use the electronic tacho pickup
4. Place the IT probe into the airflow into the engine
Interestingly WRC when they run these cars run them a little differently and (thanks to Alan, owner of WRC) we ran the car with this set up as well to replicate the test as accurately as possible.
WRC recommend:
1. Run the car in 4th gear
2. Use standard tyres pressures (Chris were 35psi when we measured them)
3. Use a manual tacho meassurement (46.88, measured as 128mpg at 6k rpm)
4. Do not use the IT probe
No these are different settings and I make no critical comment whatseover as to why this set up is used at all. They are different to what Dyno Dynamics instruct but I am sure all for good reasons without any allegation of cooking figures. Vauxhall wanted to test the car so we wanted to re-test suing the same method to put our minds at rest that we'd done nothing wrong when we ran the car initially.
The charts show a massive difference:
There are lots of things worth noting but by far the greatest issue (and the explanation for the different results from when we tested the car initially) was the issue of the car bonnet being open or closed. Dyno Dynamics suggest that bonnets should be closed as it more accurately reflects road conditions so thats how we tested it. When we saw WRC's figures we asked how and when they mentioned the bonnet up issue we re-tested it and came up with broadly similar figures to them.
That explains the mystery, however it does open up another debate on the issue of bonnets. I've asked Chris to measure his IT and engine temps when he's driving hard to see how they reflect those temps measured on the dyno, hopefully he can post those up and we can see how they compare. On the one hand we can't replicate the airflow seen on the orad in a dyno cell (even those as well cooled at WRC - 120,000cfm or ours - 137,000cfm) so there is an argument that running the car with the bonnet up is more reflective. Conversely when a car is moving the body generates a postive airpressure in front and air does not flow freely around the engine bay but passes around the car so running it with the bonnet closed is more representative of the open road. Its an interesting subject.
As most people here know Chris (BO55) has had some work done on his car and he came to us (Thorney Motorsport) to do some measuring. The numbers that came out were not as high as he was expecting and (via some fairly unpleasant name calling, not by Chris I add) it came to the result that further testing at another dyno was needed to put the matter to rest.
Chris went to WRC in Silverstone where further runs were done (paid for by Vauxhall, which was nice of them) and the numbers were (I believe, I've not seen the charts) were circa 400bhp (401 I think). Seeing as at TMS we 'only' saw 358bhp (at the wheels) I asked Chris to come back so we could run the car again if there was any discrepancy (which obviously there was).
In between this time I contacted Dyno Dynamics to get their official stance on how to power measure SC Monaros (seeing as Dyno Dynamics are Australian I took the view they know what they're doing) and their instructions were thus:
1. Run the car in 3rd gear
2. Inflate the tyres to 50psi
3. Use the electronic tacho pickup
4. Place the IT probe into the airflow into the engine
Interestingly WRC when they run these cars run them a little differently and (thanks to Alan, owner of WRC) we ran the car with this set up as well to replicate the test as accurately as possible.
WRC recommend:
1. Run the car in 4th gear
2. Use standard tyres pressures (Chris were 35psi when we measured them)
3. Use a manual tacho meassurement (46.88, measured as 128mpg at 6k rpm)
4. Do not use the IT probe
No these are different settings and I make no critical comment whatseover as to why this set up is used at all. They are different to what Dyno Dynamics instruct but I am sure all for good reasons without any allegation of cooking figures. Vauxhall wanted to test the car so we wanted to re-test suing the same method to put our minds at rest that we'd done nothing wrong when we ran the car initially.
The charts show a massive difference:
There are lots of things worth noting but by far the greatest issue (and the explanation for the different results from when we tested the car initially) was the issue of the car bonnet being open or closed. Dyno Dynamics suggest that bonnets should be closed as it more accurately reflects road conditions so thats how we tested it. When we saw WRC's figures we asked how and when they mentioned the bonnet up issue we re-tested it and came up with broadly similar figures to them.
That explains the mystery, however it does open up another debate on the issue of bonnets. I've asked Chris to measure his IT and engine temps when he's driving hard to see how they reflect those temps measured on the dyno, hopefully he can post those up and we can see how they compare. On the one hand we can't replicate the airflow seen on the orad in a dyno cell (even those as well cooled at WRC - 120,000cfm or ours - 137,000cfm) so there is an argument that running the car with the bonnet up is more reflective. Conversely when a car is moving the body generates a postive airpressure in front and air does not flow freely around the engine bay but passes around the car so running it with the bonnet closed is more representative of the open road. Its an interesting subject.
thorney said:
Thats true is you accept that the correct way to run cars on a dyno is with the bonnet up, I personally do not. However I agree it would be nice to see how a non SC Monaro runs with the bonnet up rather than down so we can see comparable figures.
Mine was run at SRR with the bonnet up on a Dyno Dynamics.
This was with headers and catback. Obviously a different car, different days etc though.
How does that compare with the previous result BO55 has at TMS?
Thanks for that John, Makes Interesting reading
We have always run the cars as WRC do, bonnet up and 4th gear in the monaros/vettes (due to the 20bhp or so lower figs you get in in 3rd on these particular cars). Something that does not affect the new vette which has different gearing. And unless the thing has 500+bhp, we run standard tyre pressures..
Good figs though, the 410bhp at the wheels IMHO means its a 500bhp car (thats what the new 500bhp vette makes at the wheels)
We have always run the cars as WRC do, bonnet up and 4th gear in the monaros/vettes (due to the 20bhp or so lower figs you get in in 3rd on these particular cars). Something that does not affect the new vette which has different gearing. And unless the thing has 500+bhp, we run standard tyre pressures..
Good figs though, the 410bhp at the wheels IMHO means its a 500bhp car (thats what the new 500bhp vette makes at the wheels)
I think the bonnet up/down debate is worthy of a long debate. For us the level of airflow we have actually makes it a little unsafe - the bonnet literally is pushed back so we need to have a member of staff holding the thing on to stop any damage! It also means that any engine issue/fire is uncontained, with the bonnet shut there is a level of defence it offers.
I'll dig up the charts that Chris did earlier (they maybe in the thread somewhere).
I'll dig up the charts that Chris did earlier (they maybe in the thread somewhere).
VXR_Daz said:
Some good work there Chris and John, well done for getting to the bottom of it 
Only problem is that it makes a comparison between pre-SC and post-SC difficult now (unless you used a similar setup for BO55's pre-SC which doesn't sound like you did)
Only problem is that it makes a comparison between pre-SC and post-SC difficult now (unless you used a similar setup for BO55's pre-SC which doesn't sound like you did)
I'm sure there are plenty of header equiped cars available to prove this.... Looks to Mose
(well, we did have identical Stage 1 figures)thorney said:
I think the bonnet up/down debate is worthy of a long debate. For us the level of airflow we have actually makes it a little unsafe - the bonnet literally is pushed back so we need to have a member of staff holding the thing on to stop any damage! It also means that any engine issue/fire is uncontained, with the bonnet shut there is a level of defence it offers.
I must admit, the engineer holding the bonnet down did look a bit white-faced.... scared and cold.... in a 135,000 cfm chamber, it get's damn cold
thorney said:
I'll dig up the charts that Chris did earlier (they maybe in the thread somewhere).
Pre S/C
Edited by BO55 VXR on Friday 1st December 19:29
One thing though....this is how real information is learnt and shared when it comes to tuning cars. Develop a new product, test it, verify it and if that verification is inconclusive then work with the relative parties to learn how and where figures can be ascertained and confirmed. Ranting off and making unsubstanticated accusations is where this whole process went wrong in the first place so I'm pleased that we've managed to turn this around to a more productive sharing of information. However I have to say, the only people who put any effort into this testing process at all have been Vauxhall, us, WRC and not least of all Chris himself.
I'd be happy to state that the kit as per Chris' car is certainly generating 500bhp at the flywheel..........but only with the bonnet up
hehe.
I'd be happy to state that the kit as per Chris' car is certainly generating 500bhp at the flywheel..........but only with the bonnet up
hehe.
thorney said:
One thing though....this is how real information is learnt and shared when it comes to tuning cars. Develop a new product, test it, verify it and if that verification is inconclusive then work with the relative parties to learn how and where figures can be ascertained and confirmed. Ranting off and making unsubstanticated accusations is where this whole process went wrong in the first place so I'm pleased that we've managed to turn this around to a more productive sharing of information. However I have to say, the only people who put any effort into this testing process at all have been Vauxhall, us, WRC and not least of all Chris himself.
I'd be happy to state that the kit as per Chris' car is certainly generating 500bhp at the flywheel..........but only with the bonnet up
hehe.
I'd be happy to state that the kit as per Chris' car is certainly generating 500bhp at the flywheel..........but only with the bonnet up
hehe.
....and I am now happy to put that issue to rest.... and once again, thanks to all who assisted in resolvng my issue
So, bonnet up or bonnet down.... let the games begin
Edited by BO55 VXR on Friday 1st December 19:32
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