R500D on the dyno

[Doc007]

Does anyone have a copy of the R500 Duratec dyno readout?

I'm curious as to what the bottom end looks like.

[David_Long]

That question is a bit of a can of worms. I don't know if this is of any help but it's the evolution of an R400 engine to the R500 spec and then beyond. Although not a factory R500, it was based closely as we could to that engine (red on the graph). It's all wheel BHP, so you need to add the losses to them for flywheel BHP. It also just a representation as it is a compilation of several dyno runs on different days.

WRT the R500, it was disappointingly poor at the low end with the R400 spec doing better. What became clear during the development was how bad the Caterham's exhaust was at the time. 

[Doc007]

That's interesting , David. Thank you. So, assuming a 15% loss that would give you around 277bhp. I don't suppose you have any torque figures? That's what I'd really like to see. What layout is the "BTB" exhaust? Is it a 4-2-1? And if so, did you notice an improvement in the mid-range? Was it very expensive/noisy/able to be fitted with a cat for MOT?

Thanks

[David_Long]

Here's the original R500 graph with torque - with (blue), and without (red) the BTB exhaust. Also it's worth saying that all these runs were not mapping sessions but power checks, for competition reasons - hence wheel power and  engine RPM on the graph is estimated from wheel speed.

And yes, the BTB was a 4:2:1 and slightly larger bore. It was responsible for transforming the mid to low range of the R500 graph. What was a surprise to us was why the R400 was so good with the standard exhaust. Best guess was that the exhaust was just a little undersize for hotter cams of the R500. Although the 4:1 is seen to kick in above 6000 rpm, the whole curve seems to be pulled down by some exhaust issue. 

The BTB exhaust wasn't cheap and was designed by Simon Armstrong who did all the R500 heads. I think he knew what was required, but was probably restrained by Caterham's resources at that time. It has a racing Cat in the silencer box, but I've never put it through an MOT .

[Doc007]

Thanks David. That's really helpful. Could you just confirm that the addition of the exhaust resulted in about 30 more torques at around 4K? That is exactly what my car needs. My 420 spec engine was much more 'fun' at low speeds with a cheeky slide coming out of a T-junctions and made more torque than my 266bhp engine until about 4.5k. 
Does your exhaust fit in the standard side skin/require any modification/cause any problems on track days?

If you could give me an idea on price and any contact details I'd appreciate it. May a PM...

[Shortshift]

Here () is  a set of curves from a mapping session carried out on my R500D by Steve Greenald (of "Two-Steve's" fame) on Luke Stephen's rolling road facility last year. 

The spec is standard R500 Duratec (2012 build) using the external carbon-fibre air intake over a foam filter, with the only non-spec item being a Raceco titanium silencer in place of the standard Caterham R500 exhaust system.  I should add that the engine was running 10W-60 oil so would probably have produced an additional couple of horsepower if it had been filled with 5W-50 as per Caterham's recommended oil specification for these engines.

It's worth confirming that the driveability (as well as top-end performance) was transformed by Steve's handiwork.  As is always the case, in my experience.

James

 

[Doc007]

Thanks James. It does seem that the R500 has a relative lack at the bottom end compared to the 420. To be expected I suppose. 

I'm currently looking at options to boost the mid range and David's exhaust looks to be a real contender.

I'll keep you posted.

[Doc007]

No idea why it got flipped or how to unflip it. You can see where the 420 (dotted) and Cosworth torque lines cross at around 4.5k. Steve Greenald did a fantastic job of smoothing out the curves and maximising output but you're always going to be fighting the intrinsic properties of the engine.

[Jonathan Kay]

[Jonathan Kay]

PS:

"No idea why it got flipped or how to unflip it."

The Forum User Guide.

Jonathan

[Shortshift]

What's the spec of the 'red line' engine, as above?  I can see the description as 'Cosworth 265 crate' but can you shed some more light on the details?

I guess there's bound to be the traditional trade-off between better torque at lower engine speeds (as in the 420) and the higher peak power of the '265' engine.

Interesting to see some comparison curves.

James

[Doc007]

It's just a crate 2l Duratec from Cosworth. Rated at 265bhp. With Cosworth TBs and DS. Rods'n'pistons. OE crank.

[Shortshift]

Thanks - seems like a good tune, all things considered.  My engine is soft-limited at 8350rpm (or thereabouts) in the interests of longevity, whereas the Cosworth seems to be free through to 8700rpm.  Interesting, too, that the Cosworth appears to be a bit stronger than my R500 (and I understand that mine is 'a good one' for engine metrics) when it comes to mid-range torque.

James
 

[David_Long]

The final results of the BTB exhaust, mapped by Troy at Northampton Motorsport are below. BTB have made two other copies of this exhaust that I know about -  both have had good results, but it would be wrong to quote any particular figure that can ce atributated to the exhaust as there are so many factors involved. The cost was not cheap -  over £3k IIRC but it's BTCC/F1 quality, basically as good as they get. Contact Joe Ellis at BTB https://www.btbexhausts.co.uk/  

 

 

[Shortshift]

Something of a torque dip at 4,000 rpm there, David?  Great for track work, I'd guess, but I'd also imagine that could be quite an issue in everyday road driveability?

I agree that BTB's systems are wonderful, and that 4:2:1 looks terrific, but I believe they are also quite heavy compared to others that are available.

James

[Doc007]

Now that is a thing of beauty!

 

[David_Long]

It actually the CAT that does that.

[Shortshift]

Ouch!  And interesting to know, too.

James

[Doc007]

What exactly is the difference between a "racing cat" and the OE cat?

Is it required to race? Would it satisfy Mr MOT?

[David_Long]

FIA Homologated CAT's are essentially designed for racing and meet minimum standard the racing authorities will accept. They differ from road car CAT's in that the core is not as fine and they are less restrictive and generally more robust -  I suspect they are less effective too.  As far as I'm aware, all Caterham cars fitted with factory exhausts are using this 'racing' spec.