Dodge Viper GTS on the rollers

Dodge Viper GTS on the rollers

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Discussion

PeterBurgess

Original Poster:

775 posts

145 months

Friday 22nd May 2015
quotequote all
I had the pleasure of pushing the rollers yesterday with a Dodge Viper special, two stage twin turbo and 9.5 litres, first stage 1000lbs/ft and 1000 bhp, second stage 1500 bhp. I decided to keep it to the first stage to 'love my dyno'.

Pic shows the Viper on the rollers.



I decided to use the new chocks we bought for Christmas...suitable for trucks and light aircraft it said on the box! Also had straps holding the 'chassis' rear of the axle to our main door as well as the usual ones in view and downward ones at back of car.

Ran a few pulls with increasing load to spool up the twin turbos. I use ear protectors so was oblivious of what I am told is the loudest car we have ever run, 188 mph in 5th with a gear to go!
Will post graph when I get to work in an hour or so and see if the rollers have cooled down yet smile

Peter

PeterBurgess

Original Poster:

775 posts

145 months

Friday 22nd May 2015
quotequote all
Here is the power graph




871 bhp at the wheels, 54 losses gives 925 bhp at the flywheel. Max torque 962lbs/ft at wheels, 1014 lbs/ft at flywheel.


Peter

Boosted LS1

21,167 posts

259 months

Friday 22nd May 2015
quotequote all
Very nice Chap :-)

stevieturbo

17,229 posts

246 months

Friday 22nd May 2015
quotequote all
Presumably Carl's car ? He's over on the Viper section here.

Lots of very hard work gone into that one, very nice build.

PeterBurgess

Original Poster:

775 posts

145 months

Friday 22nd May 2015
quotequote all
Yes it is Carl's car. I first saw it when NMS prepped it for VMax200 (2009?) and it won!

Peter

stevieturbo

17,229 posts

246 months

Friday 22nd May 2015
quotequote all
PeterBurgess said:
Yes it is Carl's car. I first saw it when NMS prepped it for VMax200 (2009?) and it won!

Peter
I think it was around the same year he brought the car to TOTB

Stan Weiss

260 posts

147 months

Friday 22nd May 2015
quotequote all
PeterBurgess said:
Here is the power graph




871 bhp at the wheels, 54 losses gives 925 bhp at the flywheel. Max torque 962lbs/ft at wheels, 1014 lbs/ft at flywheel.


Peter
Peter,
How do you or the dyno software calculate the drive train power lose? That power lose just seems a little low to me.

Stan

PeterBurgess

Original Poster:

775 posts

145 months

Friday 22nd May 2015
quotequote all
Hi Stan

Coast down test, knock it into neutral at test speed and use negative acceleration rate. Folk argue this figure is way too low but no one seems to have any real test data on what losses really are, just a load of guesses smile

We use the wheel hp and coast down losses to compare like for like. For instance, if we get another Viper in with same tyre sizes and get double the losses we know something aint right!

Peter

PeterBurgess

Original Poster:

775 posts

145 months

Saturday 23rd May 2015
quotequote all
Hi again Stan

I think the problem is folk want to know what the flywheel power is when it is the wheel power which sends the car along, maybe this is the fault of the manufacturers for wanting to give the biggest number to the customers, remember the 60s/70s ridiculously high engine power claims?

Folk criticize the rolling road as a means of power measurement and cite super accurate engine dynos as the definitive power test tool. The rolling road is a tool at the end of the day and as long as it gives the same readings day in and day out that means it is doing its job. If we alter something and it shows the positive or negative effect the same every time then we are getting repeatable results and can use it for development work at a fraction of the time needed for engine dyno tuning.

We have invested in a 'super accurate' SF901PRO complete setup, even when this is commissioned I do not expect to get a definitive what is the difference between fly and wheels. We are getting nearer to sorting the dyno but it is sapping time and money to sort the test cell and building (not for the faint hearted 'at home in the garage' tuner). We have massive extract fan holes in the walls with suitable security doors when not in use, same for the induction fan, we also have to make the downwind side of the extraction fans safe in case of engine failure and subsequent egress of flame etc! Exraction fan holes are 750mm each, induction 650mm. The exhaust pipes are now fitted, they are 110mm tube! I attach a pic of the silencers outside my main unit after we had prepped em for wall mounting. I am guessing labour and parts will come to around £6000-7000 for installation let alone the amount three of us have invested in the dyno!





Martin spent the day with us yesterday and says 'hello' to you.

Peter

chuntington101

5,733 posts

235 months

Saturday 23rd May 2015
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Is there a build thread for this car? Would be nice to see a little more of the detail.

chuntington101

5,733 posts

235 months

Saturday 23rd May 2015
quotequote all
Is there a build thread for this car? Would be nice to see a little more of the detail.

stevieturbo

17,229 posts

246 months

Saturday 23rd May 2015
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He doesnt post too often and I think there were some a few years ago, but recently some posts appeared

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

just check the viper section.

Stan Weiss

260 posts

147 months

Saturday 23rd May 2015
quotequote all
PeterBurgess said:
Hi again Stan

I think the problem is folk want to know what the flywheel power is when it is the wheel power which sends the car along, maybe this is the fault of the manufacturers for wanting to give the biggest number to the customers, remember the 60s/70s ridiculously high engine power claims?

Folk criticize the rolling road as a means of power measurement and cite super accurate engine dynos as the definitive power test tool. The rolling road is a tool at the end of the day and as long as it gives the same readings day in and day out that means it is doing its job. If we alter something and it shows the positive or negative effect the same every time then we are getting repeatable results and can use it for development work at a fraction of the time needed for engine dyno tuning.

We have invested in a 'super accurate' SF901PRO complete setup, even when this is commissioned I do not expect to get a definitive what is the difference between fly and wheels. We are getting nearer to sorting the dyno but it is sapping time and money to sort the test cell and building (not for the faint hearted 'at home in the garage' tuner). We have massive extract fan holes in the walls with suitable security doors when not in use, same for the induction fan, we also have to make the downwind side of the extraction fans safe in case of engine failure and subsequent egress of flame etc! Exraction fan holes are 750mm each, induction 650mm. The exhaust pipes are now fitted, they are 110mm tube! I attach a pic of the silencers outside my main unit after we had prepped em for wall mounting. I am guessing labour and parts will come to around £6000-7000 for installation let alone the amount three of us have invested in the dyno!





Martin spent the day with us yesterday and says 'hello' to you.

Peter
Hi Peter,
Say Hello to Martin for me. smile

I was not questioning the out of the dyno. Just the wheel to flywheel conversion. Just out of curiosity does your software correct to SAE J607, SAE J1349 or something else.

When you are fully up and running I would be interested in the results of your SF against you old dyno. The SF engine dyno software produces a high corrected HP than the standard SAE J607 does.

I do not know if you have ever used the acceleration part of my software? It is based on SAE J607 correction and wheel torque. smile

Stan

PeterBurgess

Original Poster:

775 posts

145 months

Saturday 23rd May 2015
quotequote all
Hi Stan

Not tried the torque calcs on your program yet. Dynocom correction we use is to SAE J1349.
We haven't tried the Windyn software which came with the SF901 yet, may consider the Performance Trends SF901 specific software.
http://performancetrends.com/super_flow_dyno_data_...

I feel folk think transmission losses are more than they really are. A friend who worked at Rover told me if people really knew how little was lost through transmission they would be surprised! We think the real culprits for power losses are tyre width, compound and speed, hence the 50+ bhp losses with the Viper..188 mph and very very wide tyres! Anyone who does not make allowance for tyre speed and width and compound is weeing into the wind with transmission loss percentage guesstimates.

We have rigged up the dyno cell so we can hopefully run full ex systems as will be used in the car to test engines.

Peter

v82fas

158 posts

114 months

Saturday 23rd May 2015
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Lucky enough to have seen this viper in the flesh more than once! There is a video apparently of this dyno run...anyone have a link???

Dr-Bob

6,629 posts

259 months

Saturday 23rd May 2015
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Seen this car a few times and the attention to detail is awsome. ...
Carl even helped me build my Supercharged Viper RT/10..


Glad all the eork paid off Carl..

Stan Weiss

260 posts

147 months

Saturday 23rd May 2015
quotequote all






Peter,
If you look at this, it talks about 85% mechanical efficiency. If you look at the Windyno picture you will see that SF somehow calculated a mechanical efficiency and uses that in their correction calculations. I can not say which is the better method.

Stan

Edited by Stan Weiss on Saturday 23 May 20:40

PeterBurgess

Original Poster:

775 posts

145 months

Saturday 23rd May 2015
quotequote all
Thanks for that Stan, it is a minefield isn't it? very difficult if not impossible to compare anything from dyno to dyno to rolling road I reckon.

Peter

stevieturbo

17,229 posts

246 months

Saturday 23rd May 2015
quotequote all
PeterBurgess said:
I feel folk think transmission losses are more than they really are. A friend who worked at Rover told me if people really knew how little was lost through transmission they would be surprised! We think the real culprits for power losses are tyre width, compound and speed, hence the 50+ bhp losses with the Viper..188 mph and very very wide tyres! Anyone who does not make allowance for tyre speed and width and compound is weeing into the wind with transmission loss percentage guesstimates.
Problem I see with a coastdown...It's a completely unloaded test so I dont see ohw it can be in any way realistic about drivetrain loads

The tyres wont be rammed into the rollers the same way, the gears arent loaded the same way etc etc. When you're on the power everything is different compared to the coastdown, and most seem to agree the higher the loads/power, the higher the drivetrain losses
So a coastdown has to always yield a fairly low figure.



Stan Weiss

260 posts

147 months

Sunday 24th May 2015
quotequote all
Stevie,
Thanks for bring me back to this (I went off on a tangent). What is happening is we are not measuring most of the transmissions power lose. While the manual transmission is in neutral during the coast down the only thing that is turning is the output shaft and in some transmissions the reverse gear.

Stan