JPE Power output

[Anthony]

Just curious, as Aves post on 218/235 spec engines suggests that an ideal inlet and exhaust is needed to achieve output.

 

From my experience on the Swindon dyno, a respected 4;2;1 exhaust design needed to be replaced with different primary lengths to achieve the power output.

 

Is it the same with JPE, ie 250 bhp is achieved with different exhaust/inlet and when it goes into a 7 the output may be lower ?

 

 

 

Anthony

[Piers7]

I'd heard that the JPE engines never actually made the claimed 250bhp. The best they ever had was something like 244bhp IIRC.

 

Superlight #115

[Peter T]

And very peaky power delivery.

I think Mike Culmer has a dynoe graph that shows this.

 

 

[kenny.]

Always interested me about the claimed 250bhp. I remember owners in the early days refuting the car gave anything like and also read this from knowlegable sources.

 

As I've never owned one I just can't comment and don't know the truth.

However a well known motorsport/engine building friend put together an XE which gave over 220bhp at rear wheels on a notoriously mean r/r. I'd probably equate that to somewhere near 250bhp???

 

After studying the official spec. of the JPE engine and compared to what went into this blokes there was no comparison in all honesty.......he had fully blueprinted/ trick headed ,steel cranked, expensive unit with all the proper bits etc etc. A spec quite a bit higher than the JPE's to achieve the same power ........never did get my head around that one but would be interested to hear what people think.

 

Cheers,

Kenny

 

 

Ex HPC, Ex SLR400 and now proud owner of noisy, vulgar,spitting, popping and banging ex race x/flow bought in a moment of madness after a 5 year sabatical.

[andy_h]

During my RR session Tom Ariey said he'd previously tested a Caterham which achieve 250BHP but it had £30k spent on the engine alone to do it!!!!

 

 

White road legal 2.0 HPC VX race car 😬

[kenny.]

Yep theres bhp and proper bhp 😔

Remembering back to the 80's early nineties with my first 7, there were firms offering 1700cc x/flow motors specced at 135bhp (a la supersprint) for very, very little money.

I built one and it cost more in parts alone than these offerings .......but it did give the power.

There were lots of groans at the time of these cheaper motors showing 70-80bhp on the r/r which caused a bit of a stir.

 

Kenny

 

Ex HPC, Ex SLR400 and now proud owner of noisy, vulgar,spitting, popping and banging ex race x/flow bought in a moment of madness after a 5 year sabatical.

 

Edited by - kenny. on 1 Jul 2008 13:04:07

[Peter Carmichael]

The usual internet muddle has people using all sorts of bases to arrive at a power figure from the actual measurements made on the rolling road. Difficult to sort out the facts from the chaff, especially in retrospect on hearsay.

 

If you introduce a constant into the equation like someone like Tom Airey etc. describing all the cars they have seen on the rollers over the years it gets a bit more valid.

 

I think the Caterham manifold on the JPE was a poor choice, with a significant bend in it. I think it is well known in the Vx tuning fraternity for throwing away a chunk of power.

[Anthony]

Hi Kenny,

 

Fully agree that other engines (including Swindon built) can deliver 250 bhp+

 

Suspect there is 5-10 bhp to be gained in an exhaust - certainly was with my new engine

 

IIRC the JPE engine also retained valve std springs ? When I built my first XE engine I ended up with the wrong cams and despite huge expense ended up with 230+

 

 

[kenny.]

Peter there will always be an "internet muddle" or for that matter a real world muddle when people try to convert their r/r results (which vary form road to road) to flywheel figures.

 

I think the bottom line is manufacturers in the past have been guilty of stating an optomistic figure and encompassing it in the sales splurge when in reality it is not to the letter true.

 

Also the chap mentioned here on this thread re. the rolling roads Mr. airey, is no doubt a great bloke and knows his stuff but there are also other guys who you can set you store by as well.

 

Kenny

 

Ex HPC, Ex SLR400 and now proud owner of noisy, vulgar,spitting, popping and banging ex race x/flow bought in a moment of madness after a 5 year sabatical.

[Paul McKenzie]

The JPE 250 power output was IIRC achieved by Cosworth using a different inlet manifold and exhaust. The controlling factor on Xe's has always been 'breathability', hence swap the standard injection for 45's on the Caterham manifold and the power increases from 155 in an Astra GTE to 175 in the standard CC set-up.

 

Next problem is the 'dog-leg' (to clear the chassis rail and allow the carbs to be horizontal) CC inlet manifold which tends to horrify tuners. Mine alloy welded inside the manifold and then gas-flowed it to get as straight a shot as possible into the inlet ports. A better solution obviously would be a straight inclined manifold with after market injection or DTH throttle bodies.

 

Iam sure the JPE did produce 250, but not in the CC installation.

 

Paul

 

 

[Peter T]

The JPE exhaust was pretty poor in design with the extended silecer. It did not have equal matched primaries and was a small bore compared to what people use now on trusted engines around 250bhp +.

[Jon Stewart]

What would be the best exhaust system 🤔

I've been looking at the H&S through the bonnet type and wondered what the opinions were on these (apart from looks )

 

Jon

[I reply to every thread]

I think that the general consensus is that the H&S system a la K2RUM with equal length primaries is going to be the best if you can live with the bonnet exit

[Stationary M25 Traveller]

Like this or better still - this.

 

Edited by - Stationary M25 Traveller on 2 Jul 2008 15:52:46

[captain chaos]

My BTB/SBD system gave pretty good results and exited thru and enlarged side skin hole. The headers are pretty much equal in length aswell.

[k.russell]

i have the extra long JPE manifold on my HPC here

i don't think the diameters are too small although i appreciate that the 4-2-1 is a better design. i have a larger silencer on now though.

I fitted the SBD stainless system onto my friends HPC, very nice bit of kit £££££, only problem is it requires quite a short length of silencer as the primary and secondaries are very long when they come out of the side skin hole. we had to cut down and modify his Raceco to fit, Sorry Mike

 

Kevin R

 

black(but sometimes orange)-ali HPC

here

[k.russell]

the JPE manifold had better matched lengths than the standard VX race exhaust as on Johns here

and Rogers cars here doesnt stop Rogers car from being one of the quickest sevens on trackdays

 

Kevin R

 

black(but sometimes orange)-ali HPC

here

[Alex Wong1697456877]

The JPE engine is not peaky. It's a myth.

 

Roger's Swindon JPE engine (running Jenveys instead of Weber Alpha, still with the Caterham inlet manifold) wasn't peaky. It was a very progressive power delivery.

 

Mine is running the full weber alpha kit and has DaveK's old custom made equal length primary 4-2-1 exhaust on it and it isn't at all what I'd call peaky. What it does have though is a flat spot where the power dips at about 4000 rpm - this can be frustrating if you hit it coming out of a slow corner.

 

Eric Pasture at Swindon told me my engine produced 249BHP on their dyno using the Weber Alpha injection and their exhaust rig which was designed to be equivalet to what the JPE cars had on it.

 

If I'm honest, I don't think I'm getting 250BHP but I don't think it's as far off it as some of the wild claims made by some on here.

 

Somewhere I have a Dave Walker article about the different inlet configurations on an XE and it concluded that the kinked Caterham manifold actually produced more torque than the DTH tapered systems. Maybe for outright BHP, the straight systems are better but I don't think the kinked manifold is as detrimental to power output as you might think.

 

On track, there's not much between a K R500 and a JPE in a straight line. The R500 may have less power, but it is also alot lighter. The one thing that makes it difficult to compare id corner exit speed. A well driven R500 will appear alot faster because of the exit speed. A badly driven one I can pass as if it had 50BHP less than me.

 

Edited by - Alex Wong on 2 Jul 2008 23:58:18

[Bob Simon]

Kevin,

 

I have the JPE exhaust as well. It seems to work well with Jenvey 48mm tapered TBs. There's a little torque hole at 4k but it comes on like gangbusters at 5K

 

The JPE can is a little LOUD for my liking. I see you have fitted a larger zorst. What make is it? Repackable?

 

-Bob

94 HPC VX Evo III

 

[k.russell]

Hi Bob, i made up the silencer myself, it is re packable and works well but wish i had made it a little larger diameter and a bit longer, i am in the process of making an under slung rear exhaust to make the car even more stealthy, hopefully. here

 

Kevin R

 

black(but sometimes orange)-ali HPC

here

[Jon Stewart]

So it would be more beneficial to keep my system here and bin the carbs 😳

[Peter Carmichael]

Roger's Swindon JPE engine (running Jenveys instead of Weber Alpha, still with the Caterham inlet manifold) wasn't peaky. It was a very progressive power delivery.

---

 

The only time I drove the swiftmobile was at the Curborough handling test we did for Low Flying. I'd describe Roger's car as being very peaky at that time. Distinctly ordinary until the last 1000 revs and then ballistic. I don't know what spec it was running.

[Anthony]

Jon,

 

Binning the carbs would be a great but expensive plan. Suggest you leave it as it is and enjoy

 

On the exhaust, there will always be a compromise between output and noise reduction, but I echo Aves comments about exhaust exit via bonnet ala K2RUM, and Swindon recommended a brilliant company in Slough, who make exhausts to match the dyno rig exhaust

[Jon Stewart]

Hi Anthony,

 

I think i know who you mean

I have been given a good quotation for a full sytem from H&S - 50% less than an SBD system

 

[I reply to every thread]

I have the standard caterham competition headers but I had H&S alter the collector so that the diameter of the rest of the system could be increased from the collector outlet back. I then have an H&S repackable silencer which is a very well made piece of kit - if a little heavy. The through the bonnet option was just a step too far for me.

 

Edited by - AVES on 3 Jul 2008 09:32:08