321freeflow Posted April 12, 2005 Share Posted April 12, 2005 This week, I'm going to be dyno-ing a new design exhaust for the K-engined Elise/Exige. The engine builder tells me a "guru" informed him that Caterhams, because of their short run of exhaust regularly show 20bhp more than the Elise/Exige!! Now, I'm willing(reluctantly), to believe that a Caterham exhaust versus a STD Elise/Exige exhaust MIGHT show SOMEWHERE on the curve a 20bhp gain - ie a spike on the Caterham curve coincides with a dip in the Lotus curve - but never a 20bhp on the peak reading!! My question is - how many 230bhp K-engined Caterhams are out there? (I say 230bhp because the Exige I'm using is showing 210bhp at the mo). Link to comment Share on other sites More sharing options...
Racingshoe Posted April 12, 2005 Share Posted April 12, 2005 Quite a few. The R500 is 230hp as standard, and the new 1900k's that have been built this year have been nudging 245+ bhp ! Rik Robarts - bl**dy bright orange 1900k here Link to comment Share on other sites More sharing options...
Myles Posted April 12, 2005 Share Posted April 12, 2005 I'd have thought the gains are partially due to a simpler, straighter exhaust run - i.e. less convoluted piping than on the Elise rather than a *shorter* exhaust length Project Scope-Creep is underway... Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Bob Corb Posted April 12, 2005 Share Posted April 12, 2005 I'd say every R500 (50 or so of them?) will make 230BHP and probably 10-15 modified cars. I guess the difference is mostly due to the lack of constraint on our exhaust systems due to the fact its outside the car. The fact that we run no cats and very straight systems with long/large bore absorption type silencers will help reduce back pressure but I cant believe it would make 20HP difference. How much do PTP get out of the Evo engine in their elise demo car? 220BHP isn't it? Thats 10BHP down on an R500. Sounds more realistic. Out of interest, whats your design? 4-2-1? R500s run 4 -1 at pretty much the optimum size for peak power but many have dips in the torque curve at 4500rpm due to stuffing. Most Elises run 4-2-1 so although you wont get quite the same top end (due to flow losses at the extra collectors and a bit of muddling of pressure from adjacent cylinders) you will get better midrange. Dont worry about BHP, its area under the torque curve that matter in reality (and how many exotic cars you can make eat humble pie on trackdays!! 😬) BC Link to comment Share on other sites More sharing options...
321freeflow Posted April 12, 2005 Author Share Posted April 12, 2005 Yes, I know the Caterham site states 230bhp for the R500 but is that "real world" - at the wheels? Sorry, should have made it clearer, my system runs straight to the rear valance on the Elise/Exige cutting out all the 180 bends etc. Link to comment Share on other sites More sharing options...
321freeflow Posted April 12, 2005 Author Share Posted April 12, 2005 Yup - 20bhp is prolly an unrealistic expectation(he says, sweating)! The manifold is a 4-2-1 design but with the collectors are "stacked" ie no secondary pipes at all - works for me! Link to comment Share on other sites More sharing options...
oilyhands Posted April 12, 2005 Share Posted April 12, 2005 There are at least 25 230BHP+ Caterhams , I have prepared heads for at least that many and for around 20 Elise/Exige variants. The engines have been pretty much identically specced and have consistently made between 10 and 20BHP less when installed in Elise/Exige configurations. We have tried various straight exhausts with no 180 degree bends, side exits etc, in fact around half a dozen different configurations but the peak power is always shy of the figures seen in Caterhams. That said, Steve Butt's 1900 Elise made 245BHP and 175lb/ft yesterday at Emerald which is by far the most powerful K engined Elise I have seen. I'm sure Steve will be happy to talk to you since he and Dave Walker are going to try the effect of several exhaust configurations on the same engine on an engine dyno to see if the power loss is real between exhaust types of whether it is some other installation related issue. Oily Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 It was true about the 20bhp difference.... I have been tuning my Elise since 1998, and every engine spec I have tried has always been beaten by Caterhams running the same spec, with the same level of head porting by the same porter (Dave Andrews) on the same rollinng road (Emerald). No-one was really sure why...and the only real differences were that the high powered caterhams are usually dry sumped, and the obvious exhaust system. I copied a Caterham manifold for dimensions and released 30bhp from my engine of the time for just the exhaust system change - so it can be seen that the correct lengths and diameters to match your cam timing and induction do make a whopping difference, but that change still only gave me 220ish bhp, not the 235+bhp that the Caterhams were getting. I fitted a dry sump but gained nothing, except reliability and 10k of weight! Dave Walker at Emerald has almost finished his dyno cell, and had planned to put this issue to bed once and for all by running the same 1.9k with both the Elise and Caterham exhaust systems that have the best results...and also try different induction, etc.... But now there is no need, because yesterday at Emerald: *Elise beats Caterham shocker* From a DVAPower head and Scholar 1.9k block, I had a repeatable 245bhp, found on several back to back runs where the map was being tweaked to get the AFR spot on everywhere. It only managed 172lbft compared the mid to high 170s that several Caterhams have managed, but I can't have everything !!! This wasn't a case of "let let the car cool down, open the doors, and do one power run so we can tell everyone".... And all we had time to do was map it and try a different trumpet length combination from that which I arrived with. Cam timing wasn't played with, nor was my exhaust system - I have a cat replacement pipe that is 2.25" OD where as the manifold and silencer are 2.5", so there might be losses due to that - or there could be gains..will have to wait and see until I can get back to Emerald to do some fine tuning! I put the great results down to the head porting by DVAPower, and finally arriving at a good match between cam timing, manifold/exhaust system and induction. Thanks also Dave Walker at Emerald for working his magic on the rollers, base power run after mapping was only 234bhp/173lbft.... Chuffed of Abingdon :) Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 Looks like Dave and I were posting at the same time!!! SteveB Link to comment Share on other sites More sharing options...
elise_s1 Posted April 12, 2005 Share Posted April 12, 2005 Well done Steve! *thumbup* *thumbup* Must be because of the new thermostat! cheers Carlo Link to comment Share on other sites More sharing options...
321freeflow Posted April 12, 2005 Author Share Posted April 12, 2005 Many thanks for your input guys, much appreciated. Cheers. Link to comment Share on other sites More sharing options...
Bob Corb Posted April 12, 2005 Share Posted April 12, 2005 Just one possibility which spings to mind is air inlet upheat. Caterhams have very open engine bays with lots of cold air wizzing by, especially when the bonnet is off as it usually done during mapping. The Elise engine bay will be much hotter in general (MGFs as an extreme comparison - components start melting on hot days) so the inlet pipework and manifold will heat the air entering the engine causing reduced density etc and thus power will be lost. A back to back dyno run would have showed this difference. Link to comment Share on other sites More sharing options...
oilyhands Posted April 12, 2005 Share Posted April 12, 2005 We had reckoned this was a factor so we have tried various ductings etc. to no avail.. Oily Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 Interestingly, I have an airbox and also a casing around my filter which is fitted to the side air intake, such that the enigne will only draw air from outside of the engine bay. DW pointed a large fan at the side of the car to blast cold air at my air intake. He does similar for caterhams, pointing the fan at the filter. When we changed trumpet lengths we did the first run without the airbox on and gained about 4 bhp from the trumpet change. Once we knew it worked well we put the airbox back on and then gained another 8bhp - probably a combination of pulse reflections (or whatever the technical term is) and guarenteed cold air from outside of the engine bay... SteveB Link to comment Share on other sites More sharing options...
V7 SLR Posted April 12, 2005 Share Posted April 12, 2005 I have to say, for someone who does all his work by hand, DVA's heads are bloody consistent. Just want to see how Mick gets on now... Great result Steve. I haven't forgotten I promised to give you my exhaust dimensions but I was struck with the lurgy on Friday and am still in bed (the joy of wireless LANs). Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 Yep - people can post all they like about one head porter being better than another...but the rolling road results speak for the quality of the porting, and we have a nice consistant set of results at Emerald from DVA heads compared to others! I'm still interested in the bore and lengths of the manifold you're using...although they don't seem to be so important now DW and I stumbled on the "missing link" that used to give Caterhams more power.... SteveB Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 PS get well soon Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 PS get well soon Link to comment Share on other sites More sharing options...
V7 SLR Posted April 12, 2005 Share Posted April 12, 2005 Oh God I feel like death today... and that's an improvement on the past few days. ☹️ Anyway, I'm now curious about Mick's engine because you and he (and JJ I think) have 1mm larger inlet valves to me, and you all (now) have the same exhaust valve size as I've been running since my original port. I suspect you'll get more power from cam timing to 140/115. Link to comment Share on other sites More sharing options...
oilyhands Posted April 12, 2005 Share Posted April 12, 2005 Only Mick and Steve have 33.5mm inlets... Oily Link to comment Share on other sites More sharing options...
V7 SLR Posted April 12, 2005 Share Posted April 12, 2005 Yes, of course. I keep getting confused. Think it's the fog in my head... Link to comment Share on other sites More sharing options...
SteveB Posted April 12, 2005 Share Posted April 12, 2005 ...and the bent valves.... SteveB Link to comment Share on other sites More sharing options...
V7 SLR Posted April 12, 2005 Share Posted April 12, 2005 Having seen the amount of penetration into the sides of the pockets in Mick's pistons, I am a tad worried about my own now. He (and you Steve) only have an extra half mm (radius) than me and yet Mick appears to have used most of that up digging the hole in the pocket side/wall. Anyone got a "through-the-plughole inspectomometer-thingy" I can borrow? Link to comment Share on other sites More sharing options...
V7 SLR Posted April 12, 2005 Share Posted April 12, 2005 Alex Minchin called me a half hour ago. He previously had his 1900 mapped up to 8000rpm but he wanted more because he had built it with a steel bottom end. He's now had the rest of the rev range mapped and achieved 245bhp @ 7223rpm (nice and low) and 183lbft (Wow). Different rollers but still a consistent result with the others. Link to comment Share on other sites More sharing options...
Graham Perry Posted April 12, 2005 Share Posted April 12, 2005 So has Peter C's Maximum power from a few years ago in a normally aspirated K been eclipsed with the 1900 K's ? Who now has the most power ? Link to comment Share on other sites More sharing options...
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