Missing a few BHP on my RCF

[CJP1]

I had a bit of fun today on the Dyno.
First off we strapped the car down, removed a fuse to fully turn off the abs and traction control which also took out my Speedo. I slowly ran the car up to 5th gear and then put my foot down and took it to 7000rpm. We gave it a couple of runs and it produced 445 & 447bhp so I’m a few bhp down.
As I didn’t know what speed I was doing I looked on the computer and saw 145mph😰. While I was in the car running it up it didn’t bother me but when I saw that figure I got Chris @ CCtuning to take the second run😂. 
Chris said it looked like it was running a little rich but first off I’m just going to check the air filter to make sure it’s in decent condition as I’ve only had the car a couple of months and then I will go from there…….. tbc 

Anyone else been on the Dyno?

[Lexiguy]

No but I would love the opportunity to see how may horses are missing from my SC430!

[CJP1]

Well, if you ever travel through Derby and would like it checking on the Dyno I can ask my mate for a decent discount. 

[B1RMA]

Many years ago when I had a track prepped RX7 my car was always mapped by the engine rebuilders (an all too frequent event) on a rolling road.

What I learnt from this was that certain rolling roads set ups 'flatter' the cars output and some don't, I believe the one they used a Dyno Dynamics rolling road didn't flatter the cars output but some on the market did give rather higher readings.

So maybe these days they may be a bit more accurate than in the past.

[C.B]

Unless you are running with a bunch of other cars and they are all making the expected figures and you are not I would always take RR figures with a pinch of salt. How does the bum dyno feel?

[Pielight]

445/7 bhp is a very healthy, if not overly optimistic reading. On a dyno rear wheel bhp is being measured whereas the 471bhp quoted by the manufacturer is measured at the crank. A lot of energy is lost in the transmission (through friction/waste heat) so rear wheel bhp is always substantially less. Even chain driven motor cycles lose a surprising amount of bhp at the rear wheel known as rear wheel horsepower (RWHP) - a chain is very efficient compared to the gearbox, differential and a pair of wheels with wider tyres on a car, eg. a 165 bhp bike would typically have 135 to 140 rwhp…the loss through a car transmission is greater.

My GSF came with a dyno chart from a session the previous owner had done, and it showed 464 bhp. Realising this was overly optimistic (or power had been raised above stock) I searched forums for GSF and RCF results and cars which were stock came out at no more than around 413 rwhp and quite a few were a tad under 400.

It also became very evident that dyno results vary widely from one to another, so comparisons can’t be made unless carried out on the same machine.

In a nutshell 445 rwhp does not suggest your car is down on power. 

[CJP1]

4 hours ago, B1RMA said:

Many years ago when I had a track prepped RX7 my car was always mapped by the engine rebuilders (an all too frequent event) on a rolling road.

What I learnt from this was that certain rolling roads set ups 'flatter' the cars output and some don't, I believe the one they used a Dyno Dynamics rolling road didn't flatter the cars output but some on the market did give rather higher readings.

So maybe these days they may be a bit more accurate than in the past.

Ah, cheers for the info 👍🏻

[CJP1]

3 hours ago, C.B said:

Unless you are running with a bunch of other cars and they are all making the expected figures and you are not I would always take RR figures with a pinch of salt. How does the bum dyno feel?

Bum Dyno 🤣. Feels decent Tbf but then again I was use to a Rav4 hybrid and the wife’s NX hybrid 😂

[C.B]

3 hours ago, Pielight said:

445/7 bhp is a very healthy, if not overly optimistic reading. On a dyno rear wheel bhp is being measured whereas the 471bhp quoted by the manufacturer is measured at the crank. A lot of energy is lost in the transmission (through friction/waste heat) so rear wheel bhp is always substantially less. Even chain driven motor cycles lose a surprising amount of bhp at the rear wheel known as rear wheel horsepower (RWHP) - a chain is very efficient compared to the gearbox, differential and a pair of wheels with wider tyres on a car, eg. a 165 bhp bike would typically have 135 to 140 rwhp…the loss through a car transmission is greater.

My GSF came with a dyno chart from a session the previous owner had done, and it showed 464 bhp. Realising this was overly optimistic (or power had been raised above stock) I searched forums for GSF and RCF results and cars which were stock came out at no more than around 413 rwhp and quite a few were a tad under 400.

It also became very evident that dyno results vary widely from one to another, so comparisons can’t be made unless carried out on the same machine.

In a nutshell 445 rwhp does not suggest your car is down on power. 

Most RR calculate transmission loss to provide a crank bhp, I would be very surprised if the number he was quoting was rwhp.

[Rob RCF]

There are tons of variables that could affect peak power.

Obviously you should start with the basics like check air filter, fluids, make sure you're running it on good fuel (owner's manual states 98 RON or higher). Give it a few tanks to make sure there's no 95 RON left and to give the engine time to adjust the KCLVs (knock correction learning value).

Then you have the dyno calibration which is complicated and may not be accurate unless the dyno operator really takes the time to set everything up as perfectly as possible for accuracy. This has to be done daily since some of the variables are things like ambient temperature. Then you have the actual power pull which RCFs are known to be a bit difficult due to the high gearing and very high speeds attained at redline. Some say you must do it in 6th gear as it's 1:1, but with the speed limiter disabled, some don't take it all the way to redline (7300rpm) because they're scared of running the dyno at high speeds etc.

How does the torque curve look? Can you post the chart?

[Las Palmas]

21 hours ago, CJP1 said:

Anyone else been on the Dyno?

Yes, with a MR2 first generation and a kit-car with a 2L Porsche engine in it. Do not remember results of either, but do remember that the guy running the testing told me that for the Buggy based kit-car the power weight was similar to some of the slower cars in Tour de France.

[Neil E]

18 hours ago, Lexiguy said:

No but I would love the opportunity to see how many horses are missing from my SC430!

None, it's a 3UZ....it will be spot on at 279bhp or 282 peak power @ 5600rpm depending on how they measure it.🤣 In (almost) stock set up, mine was 281.5 bhp around 110k miles) 

 

Yes 445/7 is the measurement from that dyno on the day with the parameters set. Unlikely a rwhp figure unless the GSF is tweaked but if standard, in good tune, it is probably close to 471 at the crank. If the print-out shows the rwhp figures someone knowledgeable may be able to confirm an approximate correct adjustment for it and confirm the curve through the rev range in the gear selected is as you might expect it. As said by others above there are so many variables to set. I've only done 2 sessions on a dyno-jet so far but I understand the tester is key in the setting up of the run.

Both of the testers who measured mine said they had never seen a SC430 tested and both needed a couple of test runs first and warned it would likely be under the quoted figure. After the modifications, the second guy said the last Lexus on the rollers was some months earlier and it measured 20 bhp under the manufacturer's quoted figure. It was an LFA! I was relieved when the SC recorded a healthy improvement over the standard set up.

If you could get a group of 2UR powered Fs to do a club dyno day then it should be possible to get some useful comparative numbers. 

 

 

[Pielight]

4 hours ago, C.B said:

Most RR calculate transmission loss to provide a crank bhp, I would be very surprised if the number he was quoting was rwhp.

Don’t dynojet do rwhp only and other makes give options for either (even though default is at crank)? Motorcycle dynos always use rwhp which eliminates the fairly crude conversion guestimate that an RR needs to make to calculate crank?
As you say that number is high for rwhp, but on low side for crank. Be interesting to confirm whether it was crank up or not.

 

 

[Pielight]

@CJP1 could you confirm that your quoted numbers are at crank (flywheel) or rear wheel. 

you also mentioned 7000 rpm. Pretty sure peak bhp is at 7100 rpm. The chart done for my GSF shows a significant amount of extra hp between 7000 and 7200 rpm.

BTW There is a typo in my first post. My GSF chart reads 454.4 and not 464 as I quoted. That would see our cars virtually the same if measurement taken from same source.

[ColinBarber]

This is the official chart - peak is 351 kW at 7,100 rpm.

 GS F with detail

RC F smoothed out

[BillNick]

I have also had mine on the dyno - completely stock and also got 445 confirmed as a crank reading.

As many people has said above there are so many variables on the RR.

The Dyno I went on applies a conversion to give out the crank reading - this could include errors.

Then you have the tester themselves. I made sure he was in manual, Sport S+ and diff in Track mode but didnt know at the time that gear 5 vs 6 could make a diff. He should know but I didn't check.

But I think the biggest factor for my car was that I know for sure the previous owner used 95 RON as I asked him on my test drive and the dyno run was done only 1 month after I had also filled it with 95...........I have been religiously running Esso 99 RON ever since (about 9 months) and will be going back on the dyno as soon as my new cat back arrives (will do before and after).

Hopefully the 99 will recover some of those horses - not all but some.

[edit] Tyres...what about your rear tyres? I am not impressed with the traction from the Bridgestones currently fitted to mine, so could they slip on the dyno? Perhaps not once up to speed.

[Rob RCF]

51 minutes ago, BillNick said:

I have also had mine on the dyno - completely stock and also got 445 confirmed as a crank reading.

As many people has said above there are so many variables on the RR.

The Dyno I went on applies a conversion to give out the crank reading - this could include errors.

Then you have the tester themselves. I made sure he was in manual, Sport S+ and diff in Track mode but didnt know at the time that gear 5 vs 6 could make a diff. He should know but I didn't check.

But I think the biggest factor for my car was that I know for sure the previous owner used 95 RON as I asked him on my test drive and the dyno run was done only 1 month after I had also filled it with 95...........I have been religiously running Esso 99 RON ever since (about 9 months) and will be going back on the dyno as soon as my new cat back arrives (will do before and after).

Hopefully the 99 will recover some of those horses - not all but some.

[edit] Tyres...what about your rear tyres? I am not impressed with the traction from the Bridgestones currently fitted to mine, so could they slip on the dyno? Perhaps not once up to speed.

Personally I don't see why running in 5th or 4th would be a problem as long as the dyno operator uses the correct gear ratio, the main thing is the car gets a good run all the way to the rev limiter.

I would hope the dyno operator actually measures the losses though, presumably by shifting into neutral and coasting. Disappointing if they just estimate it.

Would be interested to know how you get on after using the 99ron long term. I'm on about my 3rd tank, was using VPower before.

[BillNick]

Ah ok so is selecting the gear ratio part of dyno setup then? Clearly I am no expert in this field...

The dyno I went on applies a conversion factor in real time - the details of which I don't know. It wasn't something he calculated himself as such, he was able to toggle between WHP and BHP on the screen.

I will definitely post my results, but wont be until march time.

I am not fitting the Invidia until after a track day I have booked on 24th Feb - sound restrictions etc....

[CJP1]

4 hours ago, BillNick said:

I have also had mine on the dyno - completely stock and also got 445 confirmed as a crank reading.

As many people has said above there are so many variables on the RR.

The Dyno I went on applies a conversion to give out the crank reading - this could include errors.

Then you have the tester themselves. I made sure he was in manual, Sport S+ and diff in Track mode but didnt know at the time that gear 5 vs 6 could make a diff. He should know but I didn't check.

But I think the biggest factor for my car was that I know for sure the previous owner used 95 RON as I asked him on my test drive and the dyno run was done only 1 month after I had also filled it with 95...........I have been religiously running Esso 99 RON ever since (about 9 months) and will be going back on the dyno as soon as my new cat back arrives (will do before and after).

Hopefully the 99 will recover some of those horses - not all but some.

[edit] Tyres...what about your rear tyres? I am not impressed with the traction from the Bridgestones currently fitted to mine, so could they slip on the dyno? Perhaps not once up to speed.

Yeah, we were definitely in 5th but not sure about sport+ tbh. I’ve always put the better fuel in so that won’t be a problem but I will get it on the Dyno again in the next couple of weeks when I get my cat back on it to see if it gives me a few more bhp 🤞🏻 

[BillNick]

2 hours ago, CJP1 said:

Yeah, we were definitely in 5th but not sure about sport+ tbh. I’ve always put the better fuel in so that won’t be a problem but I will get it on the Dyno again in the next couple of weeks when I get my cat back on it to see if it gives me a few more bhp 🤞🏻 

Same. Good luck 🤞🏼 

[Rob RCF]

6 hours ago, BillNick said:

Ah ok so is selecting the gear ratio part of dyno setup then? Clearly I am no expert in this field...

The dyno I went on applies a conversion factor in real time - the details of which I don't know. It wasn't something he calculated himself as such, he was able to toggle between WHP and BHP on the screen.

I don't know, but surely you'd at least need tyre size to calculate wheel torque and wheel speed which are ultimately what the dyno measures. Then you use the gear ratios to derive engine rpm and horsepower from that. They may have some clever ways of doing it automatically though.

[BillNick]

1 minute ago, Rob RCF said:

I don't know, but surely you'd at least need tyre size to calculate wheel torque and wheel speed which are ultimately what the dyno measures. Then you use the gear ratios to derive engine rpm and horsepower from that. They may have some clever ways of doing it automatically though.

I suspect the software asks for all those parameters beforehand or it’s all preloaded in a database of vehicles….

[CJP1]

So , I finally got my gthaus musa GTC cat back exhaust fitted and wow does it sound great and the car certainly feels different to drive. 
The reason for popping it on the dyno before having the exhaust fitted was because gthaus say that fitting this cat back system can give you more bhp. After putting it on the dyno with it installed and everything else the same I.E 5th gear and 7000 rpm it certainly produced more bhp , I then opened the valves and the final run produced 49 bhp extra. 
Here are the results which I know to some of you will mean more than it does to me. 

[CJP1]

1 minute ago, CJP1 said:

So , I finally got my gthaus musa GTC cat back exhaust fitted and wow does it sound great and the car certainly feels different to drive. 
The reason for popping it on the dyno before having the exhaust fitted was because gthaus say that fitting this cat back system can give you more bhp. After putting it on the dyno with it installed and everything else the same I.E 5th gear and 7000 rpm it certainly produced more bhp , I then opened the valves and the final run produced 49 bhp extra. 
Here are the results which I know to some of you will mean more than it does to me. 

 

[BillNick]

That’s a remarkable result. Anything else changed since the baseline run in December? Same fuel?