The long awaited result....

[Red SLR]

Picked the car up from Mikeanics this avo.

 

The result is:

 

141.2bhp

 

BUT

 

Mike says his rollers can read about 10bhp under, so the car is probibaly running nearer to 151bhp. Mike says that there might be another 5bhp somewhere.... but might take a few more hours on the rollers to get there.

 

I will go to another rolling road sometime over the next few months for another power run.

 

The feel of the engine has changed so much, it is so much smoother and the power explodes at about 5000rpm and the car really does go a lot faster now.

 

I did not realise just how much difference it has made until I went on the motorway tonight, at about 50 I booted it in 3rd gear, 4th and 5th came a lot faster than normal and the car is much better to drive in 6th now.

 

The plan now...... over the winter upgrade the valves and cams and pistons etc etc.

 

A top job by Mikeanics!

 

Simon.

 

X777CAT

[Tim Sture]

Simon

 

you should mention that the 141.2 bhp is at the wheels - might make a difference to people's perceptions..

[murph7355]

Sounds like a good result, and the *key* thing is that it feels better (and presumably sounds better!).

 

It would definitely be worth asking Mike for full plots from the rolling road. You can then put them against all the ones taken at Emerald (which include both "at the wheels" and "flywheel" figures - available on the se7ens list). Don't read shed loads into it because rolling roads can vary by a significant amount. But the shapes of the curves should give you an idea of where you're at.

 

The other good point is that you've found someone who can do you a decent job for when you carry out your other mods.

 

C7 AJM

[Peter Carmichael]

A comparison of at the wheels figures will be utterly meaningless, so see if you can get the flywheel figures.

 

You can run a car up on rollers twice back to back and get completely different at the wheels figures, because the losses in the tyres are temperature dependent. The only comparison worth doing is for coastdown loss corrected at the flywheel figures.

 

What you do know is that the at the wheels figure is less than the flywheel figure, so you have significantly more than 141.2bhp.

 

[PACR]

What exactly was done to the motor - thought you were just adding throttle bodies and new ecu to a supersport spec 1.6? What was the figure at the wheels before - if it really is the at the wheels figure. Seems like quite a jump for not a lot of work!

 

Piers

[Peter Carmichael]

what was the figure at the wheels before

 

aaaaaarrrrrghhhh

 

My

You can run a car up on rollers twice back to back and get completely different at the wheels figures

 

What gear was it in?

What tyre pressures?

What tyre temperature? (the tyre temperature changes during a run)

What ambient temperature?

What humidity?

What tread thickness?

What weight in/on the car?

Was the car strapped down and if so, how tight?

...

 

Am I getting through yet? At the wheels comparisons are meaningless unless you can guarantee that all of the above are held equal as a minimum and there are bound to be a few considerations that I haven't included.

[Paul R.]

Quote

'Seems like quite a jump for not a lot of work!'

I think if you have followed this and various threads, you will see there was a fair bit of work (it should have been easy, but was anything but straight forward). John E. and I helped and whilst the work didn't involve dismantling of the engine, it did require a lot of ingenuity and guesswork, not to mention a lot of heartache on Simon's part. Simple things like putting together the throttle linkage with no suitable instructions and finding that access to certain nuts was limited and then when assembled had to be dismantled to file the end off a stud which fowled the linkage. Certainly if we were to do the job again, it would be much easier, drawing on the experience. One tip I would give to anyone contemplating fiting of throttle bodies is 'dump the manifold studs and use cap headed bolts'. If you are contemplating a similar fitting, and undertaking it yourself, I suggest you don't underestimate the task.

Paul R.

[oilyhands]

In that context 'not a lot of work' I think meant minimal change to the engine.. not the amount of work required to install the TBs. A jump to 141 (estimated 151 because of the under-read) at the wheels even allowing for the minimum possible losses seems a large gain over standard for such a relatively small net change.

 

I'm surprised you had so much difficulty with the TBs, I've fitted a few sets with very little drama, got another 3 sets coming up shortly.

 

Oily

[Red SLR]

Right then. All I will say is the car goes a hell of a lot quicker.

 

As I did not do a RR session with it in STD SS trim then I do not know what the actual gain was. But the final figure was 141.2bhp.

 

Simon.

 

Ps - thanks once again to John and Paul for helping.

 

X777CAT

[PACR]

Chill out Peter...

 

Ever heard of the terms 'ballpark' or 'rough comparison'!!!!

 

I was just after a guide - thought there might have been a before and after comparison done - for interests sake.

 

Short of insisting every one only quotes power figures from the same engine dyno under exactly the same conditions everyone knows you are going to have quite a margin of error in measuring and quoting the power of an engine. However it would be resonable to assume that the same operator on the same rolling road with some experience would give a sufficiently usefull difference figure. And as the conditions on the road / vary as in the workshop does it matter too much? I mean if I was an unscruplus rolling road equiped tuner I might super heat my workshop for the before runs and ensure it was nicely chilled on the after runs.....

 

Oily's right - I meant as in not doing any internal engine work / changing SS cams or getting the engine out of the car. I'm sure throttle linkages can be tricky until you get the hang of it.

 

Piers

[oilyhands]

On re-reading my post it comes across as a lot more terse than I had thought while penning it.. if I've offended anyone.. unreserved apologies.

 

It would be useful to have some empirical data on the output of Simons engine after the TB fitment because it's an upgrade many people are/will be planning. It's a pity that Simon isn't closer to Emerald because a run there would give a useful yardstick against a plethora of other K series runs on the same RR (which also gives flywheel figures via a coastdown test). These are standard, modified and heavily modified cars, it would then be easier to quantify exactly what does what with the K WRT to bolt ons.

 

Oily

[Peter Carmichael]

Sorry Piers for getting on my soapbox.

 

The unscrupulous rolling road operator can just say "I think we'll run it up in fourth this time" and hey presto you get an extra 12bhp at the wheels (compared to fifth) - a cheap upgrade? No. A con job.

 

This is also an area of great misunderstanding even amongst rolling road operators. It is however a simple matter of metrology - understanding exactly what is being measured. Rolling road operators are more usually mechanics rather than engineers.

 

Now, as for Simon's figures, I am confused. Typical power losses on a rolling road (taken from the Se7en list's days at the Emerald workshop) vary between 30bhp and over 50bhp. On a set of runs on the same day with my own car, during setup, the losses in fifth gear at 7300 rpm varied between 35 and 43 bhp, depending on how long it had been since the previous run. The flywheel corrected bhp figures lined up with uncanny accuracy. An initial run in 6th gear that went as far as 6600 rpm showed losses of 39 bhp. At the same revs in a run in fifth the losses could be as low as 30bhp.

 

We are talking about figures going missing which are of comparable size to the likely actual improvement in engine performance, so I do not think you get even a *rough comparison* from an at the wheels figure. Believe what you want, but these are unsubstantiated numbers.

 

I don't want to poop on Simon's parade. I know from having set up throttle bodies on my Supersport that the power increase is noticeable and the engine manners (noise) are vastly improved. I just think the numbers need closer examination.

 

141.2?

 

Well let's start by discarding the .2 - it is false accuracy.

 

Now, what about this "underreading by 10bhp". This isn't related to it being "at the wheels". Transmission (tyre) losses are much larger than this. The engine certainly won't be producing ~170bhp, which my substantiated information on losses would suggest. How have we come to understand that the 141bhp was at the wheels? I think the rolling road operator must have applied some sort of correction or the calibration must be wildly out.

 

In fairness, I think about all that can justified from these unexplained numbers is that the engine is producing over 130bhp. From just bolting on throttle bodies to a 1.6 Supersport I would expect something like 150bhp and I believe this finger in the air estimate is more accurate than falsely authoritative numbers.

 

Now for some reassurance for Simon...

 

... the setting up procedure for the engine (certainly up to ~5000rpm) does not rely on accurate rolling road calibration and can be done from "at the wheels" figures. Finding a few extra bhp (Mike's 5) requires trim runs and correction for transmission/tyre losses - this is not possible from "at the wheels" figures without immense care regarding tyre temperature, vehicle loading and ambient conditions.

 

Your car will be set up well - enjoy it and tell everybody it has 150bhp. (which is more or less where we were when I started this, but the justification for the number is the work that has been done, rather than the price of fish which might as well be what the rolling road was calibrated in).

 

I'm trying to be helpful - honest. Misunderstanding this sort of thing can end up being a big drain on cash for zero result.sad.gif I have had this sort of debate with Oilyhands in the past and agree with what he has written - I too would be interested in getting a comparable set of data for this bolt on conversion.

 

Edited by - Peter Carmichael on 11 May 2001 12:09:50

[Hurdsey]

Simon

 

the Lancs and M/c areas of WSCC are meeting this Sunday at the

Strawbury Duck in Entwistle, why not come along and show it off,

in fact anyone with a Se7en type car is welcome.

Oh yes its from 1 till 4pm.

 

Edited by - hurdsey on 11 May 2001 12:42:15

[Tony Martyr]

Peter,

Just leave a bit of room on that soapbox and do not apolojise for standing on it.

Quoting to a decimal point on a test unit that is admitted to have at least a 7 percent error is no sense.

I think the only thing you left off the list was the power changes you can induce by changing tyre pressures and therefore rolling radius across the diff.

To be fair I am working with a Schenck 48 inch machine installed in a climatic chamber - cost 0.8million pounds, this is outside the aftermarket budget, but we still don't take seriously any wheel to flywheel calculations and our power mapping runs with full temperature control still show problems in run to run correlation.

The problem is this 'pi**ing contest we feel obliged to enter based on flyweel power figures. In the end it is how it feels and goes that counts, the number are only of use if you have to justify the expense of modification to yourself or someone else

[captain chaos]

I've been to Mikeanics today for a bit of tweaking following my Cadwell track day on tues. I spoke to Mike about Simon's car and he explained how he had to virtually re-write Simon's mapping as when it arrived a certain element had to be de-activated (I'm no expert and I've forgotten what it was) and the previous RR people had basically got nowhere near.

I've actually found Mike's rollers to be slightly conservative in comparison.

My Vx on his RR regularly gives 232 bhp at the fly-wheel. It has recorded 239 elsewhere recently.(I'm sure PeterC could explain this variation by including factors such as temp etc..) Mike felt that because he could have done with more time on Simon's car, other gains could be made aswell. I hope I am not confusing matters here for Simon but Mike confirmed the 142 to be a fly-wheel figure.

[CHRIS CLARK]

At the recent Emerald RR II session my 41,000 mile 1400 SS gave a figure of 133 BHP.I am aware of the thoughts that 'K's can take up to 20,000 miles to really settle! I'm quite happy to use this figure but realistically think the RR overeads by about 5 percent. That would give me a figure of 126.35 ish BHP. More likely I think!

I have spoken to some of the others on this session and some agree, but others just 'won't have it'! Funny how some people hang on desperately to the figures given as if they were gospel!!!!!

Me? Well mine was just done as a 'before the 1800 engine change' to give a decent comparison. You should have done the same Simon (on your same RR) to give yourself a chance of seeing what BHP increase you have made.

 

Having an edit problem here

 

Edited by - chris clark on 11 May 2001 19:35:22

 

Edited by - chris clark on 11 May 2001 19:36:41

[captain chaos]

I agree Chris, if the car is running ok then the higher relevance is the change/improvement and not just the final bhp figure. My car started at Mikeanics with 202 bhp and with correct jetting and 3d work it went up to 232. The relevance is the improvement and keep it comparative. If I had gone to another RR during the work (it was spread over 2/3 weeks) it could easily have shown an improvement where there had not been one.

 

Edited by - captain chaos on 11 May 2001 20:03:49

[Red SLR]

CC- Was at Mikes on Friday, but just missed you!!!

 

I forgot to ask him if the fig of 141 was at the wheels.

 

Any way took the car to Elvington on Saturday. Much improvement in power over 4000rpm. Car now blasts to 100 much quicker, yet to time it but I think I have taken a good second off it.(0-100)

 

Ta.

 

Simon.

 

X777CAT