North London Mike Posted August 11, 2006 Report Share Posted August 11, 2006 Hi Guys Just a quick item. I'm on SU's and off to Cambridge Motor Sport (Well, Mass Eng anyway) for a rolling Road set up and Chris mentioned twin 45's ( ) I currently get 34/35 mpg , a little more on a run. How much worse would this be on twin 45's. I had a single 45 on my Frogeye (1340cc fast road) and got 25mpg as an average!! It would need to be a LOT quicker for me to loose 10mpg Any info Quote Link to post Share on other sites
Ade-TR4 Posted August 11, 2006 Report Share Posted August 11, 2006 Hi Andy used to run Webers on the TR4 we rallied, and it was awful on fuel. It wasn't suited to stop-start rallying which most historic roads rallies tend to be. It's on HS6s now and runs very very well. The SU is better suited to a torquey, lower revving set up, which the 4-cyl engine is. If your engine is of a spec that it can rev its nuts off (ie 5,000+) for sustained periods then the DCOEs are the way to go. You will need an electric fuel pump and pressure regulator as well. I think most people that convert to webers find it an expensive operation. TR-Tony will tell you tales of derring-do involving webers and flame spitting exhausts (and slightly concerned navigators), but his engine is a steel-cranked, forged piston affair. Andy and I had good results with the SUs, often setting fastest test times. (after switching to the SUs, we thought the fuel gauge had broken as it didn't seem to plumet like before!) You pays-yer-money-and-takes-yer-choice! Cheers Adey Quote Link to post Share on other sites
7VC Posted August 11, 2006 Report Share Posted August 11, 2006 Hi, 7VC is on twin 45 DCOE's (obviously - that's what the works cars had from '63!). On spirited motorway driving (80ish, not hanging about) it will return 25mpg, but as soon as we're on a rally (the more serious UK events involving road regularities in 2nd or 3rd, and full-on driving tests) it drops to about 15mpg. The engine is fairly standard - lightened and balanced, plus a sports camshaft and a gas-flowed head, but standard crank - nowhere near as high-spec as Tony Sheach's car. BHP is about 125-130, so you may think the expense of the Webers and the fuel bills are not worth the power increase you get. Had I not wanted a works-spec car, I probably would have taken the advice and stayed with SU's as you can get more power for better mpg (provided you do the necessary with the head). Webers don't like getting hot, either - I have heat shields, but if you sit in a queue for a test after a road section, things soon get lumpy and unsettled, just when you need power! But the Webers sound awesome! I also had the flame-spitting dive-bomber experience at the beginning, but got it re-tuned as I was worried about blowing up my exhaust! Cheers, Jonathan Quote Link to post Share on other sites
marvmul Posted August 11, 2006 Report Share Posted August 11, 2006 Most Weber cars have an electric fuel pump , but a mechanical pump will do also. Webers are great : the looks and the sound. And they perform better than SU's on a race car. But, on a road TR, in what circumstances will they perform better than SU's? Quote Link to post Share on other sites
Tom Fremont Posted August 11, 2006 Report Share Posted August 11, 2006 (edited) I don't have broad enough experience to know, but the above reports of horrendous fuel economy don't square with my experience on a TR250 of ~ 150 bhp on triple 40DCOEs. I get 20-21 mpg ( U.S.) overall, equating to 23 mpg Imperial if I'm not mistaken. Anyway, the fuel tank capacity is 13.5 gal U.S. vs. 11.5 Imperial, if you want to do the math. My other perfectly stock and ( if I say so myself ) perfect-running emissions carburetored TR250 got 26-27 mpg U.S. overall, for comparison. I attribute the difference to the cam overlap, 70 degrees in the former and 20 degrees in the latter. Spark plugs were equally clean and grey on both. 23 mpg compares favourably to the P.I. according to the reports of the day, i.e. 19 mpg on the TR5. I know that Webers can be made to run fabulously without regard to fuel consumption, but it takes more diligence to optimize the settings for economy without sacrificing performance. Perhaps many stop short of this; it took me a few changeouts to achieve 25% better economy with the same performance. Racetorations do a lot of 4-cyl Weber applications; I doubt they're overly concerned about fuel economy but they may have a worthwhile perspective on this. Seems to me, if the burn is clean the fuel delivery can't be too excessive no matter what system you've got... Edited August 11, 2006 by Tom Fremont Quote Link to post Share on other sites
North London Mike Posted August 11, 2006 Author Report Share Posted August 11, 2006 Hi, 7VC is on twin 45 DCOE's (obviously - that's what the works cars had from '63!). On spirited motorway driving (80ish, not hanging about) it will return 25mpg, but as soon as we're on a rally (the more serious UK events involving road regularities in 2nd or 3rd, and full-on driving tests) it drops to about 15mpg. The engine is fairly standard - lightened and balanced, plus a sports camshaft and a gas-flowed head, but standard crank - nowhere near as high-spec as Tony Sheach's car. Cheers, Jonathan Jonathan Thanks for the input, I'm running 7VC's sister car, 93LNK but obviously without the Webers (hence the questions) she'd be great on webers...............and Clive put a tough little engine in her, 135bhp 'ish on SU's! Everybody says stay with the HS6's for low rev road use and after years on Webers its a hard choice. However Jonathan's 25mpg is exactly what I expected and on the SU's I get 35mph .......and its nice, just once, not be the first guy in the convoy to call for a fuel stop (on every trip) Thank god I haven't got £7-800 odd squid for the converion Quote Link to post Share on other sites
littleone Posted September 3, 2006 Report Share Posted September 3, 2006 Hi Mike, Sorry to add my two pence worth so late in this string, but just to reinforce the majority advice. I run a 4 with 42DCOE's, 125bhp +, (set up at MASS) and returned from a touring holiday of Italy at the beginning of this month. Reasonably careful long motorway cruising at around 70 - 80 mph returned a smidge below 30mpg overall, anything else though and I struggle to achieve 23 - 25 mpg. Serious use of revs and just forget it....... When I bought the car in 1971 the Webbers were already fitted so during her restoration in 1986 I had them restored to as new. Fuel economy was never my overriding concern as the car is a "hobby" and only gets light use and after all it is a sports car. My main concern is the way they misbehave when they get warm! Touring Northern Italy in July it was so hot that if I was forced to stop in stationary traffic in the heat of the day for more than 5-10 minutes the inevitable rough running would be followed by total loss of power as vapour lock kicked in and I would be forced to pull over and open the bonnet and wait 5-10 minutes for things too cool enough to pull away. If I was able to keep it revving enough and tease it along I could sometimes get enough cool fuel into the carbs to be able to continue. Once under way all was well. All this despite wrapping the exhaust manifold well and fitting a fairly substantial heat shield. In the UK this problem rarely rears its ugly head as severely but I have been caught out on one particularly warm summer. I think it was a Wednesday……! The cooling system is well sorted and engine temperature was no problem, just the Webbers copping a strop in the heat. With a Rally replica you will have the wing vents (which I am considering) so things should be a little cooler under your bonnet. Having always run on Webbers I have no desire to fit SU's simply to improve fuel consumption and will persevere with attempts to keep them nice and cool. I can forgive the slight low mid range lack of power for the song they sing when the wick is turned up.... But to shell out for Webbers when you must have a very well sorted setup on SU’s already, sounds unnecessary. I watched the progress on your car at that nice Mrs. Manvers little boys establishment on my periodic visits, and you have a really lovely car. Kind Regards, Paul. Quote Link to post Share on other sites
North London Mike Posted September 3, 2006 Author Report Share Posted September 3, 2006 Hi Mike, My main concern is the way they misbehave when they get warm! Having always run on Webbers I have no desire to fit SU's simply to improve fuel consumption and will persevere with attempts to keep them nice and cool. I can forgive the slight low mid range lack of power for the song they sing when the wick is turned up.... But to shell out for Webbers when you must have a very well sorted setup on SU’s already, sounds unnecessary. I watched the progress on your car at that nice Mrs. Manvers little boys establishment on my periodic visits, and you have a really lovely car. Kind Regards, Paul. Hi Paul Thanks for the kind words ref the 4, do I assume your a Manvers boy as well? Hear what you say about the heat soak. Did what you did to the Frogeye plus a massive Kenlow and still had problems. BUT I did love my 45 After my session with the SU's at Mass and my misfire, now sorted I did some long range 70-85mpg transit stages (rally speak for dual carrageways) to The Little Gransden air show, joining the Lea valley boys at Knebworth and an early morning cross country blast down from North London to Goodwood, where I found myself with the gauge between empty and 1/8th and 369 showing on the trip................ Now we all know how accurate the fuel gauges are so we mugged the first petrol on the way how and was pleased to find that she'd done 38mpg and we had over a gallon still in the tank I suppose that I could get it down to sub 35mpg if I really thrashed it So the debate rages: However, range (its not about the money) combined with the low mid range torque on the SU's is a strong arguement for keeping them. Bit like you really Paul. If I didn't already have them and had a blank sheet of paper the decision might well have been the 40's Watch this space........... Quote Link to post Share on other sites
Guest harry dent Posted September 3, 2006 Report Share Posted September 3, 2006 Jonathan Thanks for the input, I'm running 7VC's sister car, 93LNK but obviously without the Webers (hence the questions) she'd be great on webers...............and Clive put a tough little engine in her, 135bhp 'ish on SU's! Everybody says stay with the HS6's for low rev road use and after years on Webers its a hard choice. However Jonathan's 25mpg is exactly what I expected and on the SU's I get 35mph .......and its nice, just once, not be the first guy in the convoy to call for a fuel stop (on every trip) Thank god I haven't got £7-800 odd squid for the converion Mike,only 35 MPH on SU,s.I can ride my Mounting bike down hill faster than that! See you at The Clarendon Arms. Regards Harry. Quote Link to post Share on other sites
North London Mike Posted September 4, 2006 Author Report Share Posted September 4, 2006 Mike,only 35 MPH on SU,s.I can ride my Mounting bike down hill faster than that!See you at The Clarendon Arms. Regards Harry. ...............but Harry You carry a lot more weight through the corners Quote Link to post Share on other sites
rudi Posted September 4, 2006 Report Share Posted September 4, 2006 My 40 Webers bring it to a max of 30 Mpg (combined highway/shortdistance) and approx 25 mpg during rallying (2187 cc/sprint 88 cam/stage 3 head). Good low rev torque on the 40ers. regards, Rudi Quote Link to post Share on other sites
North London Mike Posted September 4, 2006 Author Report Share Posted September 4, 2006 My 40 Webers bring it to a max of 30 Mpg (combined highway/shortdistance) and approx 25 mpg during rallying (2187 cc/sprint 88 cam/stage 3 head). Good low rev torque on the 40ers.regards, Rudi Bugger, thats muddied the water Thanks Rudi (sounds like you have the best of both worlds) Quote Link to post Share on other sites
Rex Wyer Posted September 4, 2006 Report Share Posted September 4, 2006 I've heard of a Mountain bike, but a Mounting bike is new to me - what do you do, give it one ? Or does it have some padded accessory for 'er indoors to lean on ? Cheers, Alec Nice one Alec, I must admit that similar thoughts passed through my mind when I read Harry's post. Quote Link to post Share on other sites
Andrew Smith Posted September 4, 2006 Report Share Posted September 4, 2006 Nice one Alec, I must admit that similar thoughts passed through my mind when I read Harry's post. Sod it, I din't notice! Cheers Adnrwe Quote Link to post Share on other sites
Guest harry dent Posted September 5, 2006 Report Share Posted September 5, 2006 Ooops!.Fatal mistake.Mind you Mounting bike reminds me of my distant youth.Those were the days when we were relatively free. Regards Harry. Quote Link to post Share on other sites
littleone Posted September 7, 2006 Report Share Posted September 7, 2006 Hi Paul Thanks for the kind words ref the 4, do I assume your a Manvers boy as well? Now we all know how accurate the fuel gauges are so we mugged the first petrol on the way how and was pleased to find that she'd done 38mpg and we had over a gallon still in the tank I suppose that I could get it down to sub 35mpg if I really thrashed it Hi Mike, Manvers Triumph is very local to me and I have found Clive to be extremely helpful. He always makes time to discuss any problems I may have despite how busy he is. His advice and guidance has been invaluable to me. Two days before I set off to Italy I phoned him to enquire if he had a narrow fan belt in stock, he didn't, but added one to the order he was placing with his supplier and had them deliver it direct to my address. It arrived the next morning........ 38mpg !! I dream of 38mpg. I see on another thread you are considering fitting a brake servo, Don't hesitate, I fitted one in the spring mainly as a concession for my wife so she can drive me home from the pub............. Standard disks and calipers with Greenstuff pads, Brilliant.... Far from less feel I find it enhances the touch. Regards, Paul. Quote Link to post Share on other sites
North London Mike Posted September 7, 2006 Author Report Share Posted September 7, 2006 Hi Mike, Manvers Triumph is very local to me and I have found Clive to be extremely helpful. He always makes time to discuss any problems I may have despite how busy he is. His advice and guidance has been invaluable to me. Two days before I set off to Italy I phoned him to enquire if he had a narrow fan belt in stock, he didn't, but added one to the order he was placing with his supplier and had them deliver it direct to my address. It arrived the next morning........ 38mpg !! I dream of 38mpg. I see on another thread you are considering fitting a brake servo, Don't hesitate, I fitted one in the spring mainly as a concession for my wife so she can drive me home from the pub............. Standard disks and calipers with Greenstuff pads, Brilliant.... Far from less feel I find it enhances the touch. Regards, Paul. Hi Paul Yes, Clive's a good guy. Thanks for the confirmation on the servo. Decision made, next job! Just have to allocate enough beer vouchers Quote Link to post Share on other sites
graeme Posted December 30, 2008 Report Share Posted December 30, 2008 (edited) Hi, Sorry to bring this up again, but I would just like to add my experience to the above. I rebuilt my engine about six years ago, fully balanced, Powermax 87mm pistons and a Classic Racecraft fast road camshaft. Although it revved like crazy and was still eagerly accelerating at 6000RPM, it lacked any bottom end torque. The SU's were set up by an acknowledged expert which did improve things slightly but still no low torque. After a lot of research, I decided to fit Webers and today I have fitted a pair of 40DCOE Webers. The difference is a revelation, pulling strongly from less than 2000RPM and still wanting to rev upto 6000 RPM. And this is with my initial guesstimate at the required jets, so should improve even further after a session on the rolling road. Obviously it will be some time before I can check the fuel consumption but I only do about three thousand a year so not too bothered. On the subject of fuel vapourisation, the SU's have suffered on the occasional hot day in the UK when sitting in traffic, but I suspect it is more to do with the routeing of fuel pipes rather than the carbs, so I will be making an effort to route the pipes by the coolest route under the bonnet. Hope this adds to the debate but my money is definitely on Webers. Cheers Graeme Edited December 30, 2008 by graeme Quote Link to post Share on other sites
MadMarx Posted December 30, 2008 Report Share Posted December 30, 2008 I need 19 L in 30 minutes. Hope this helps. Chris Quote Link to post Share on other sites
Badfrog Posted December 31, 2008 Report Share Posted December 31, 2008 What can I say? You guys went down all the issues about Webers versus HS6. You nevertheless forgot the option of tuned HS8's. Man, are they great once you solved all the pitfalls (took me a year or so). As a bonus, once you've installed the required "D" bonnet (call Revington for a quote), your banger look like a sideways sabrina. I had a great joke on mounting bikes, unfortunately it won't translate from french. That's the true Babel curse for you. Cheers, Quote Link to post Share on other sites
Alec Pringle Posted December 31, 2008 Report Share Posted December 31, 2008 Hi Chris, that equates to 8.35 imp gals/hr. If your lap speed is 83.5mph, or 133.6kph, that's 10mpg. If your lap speed is any slower, it's less than 10mpg. Not unreasonable, by my reckoning and experience. It doesn't much matter what TR you're driving, if you're driving it hard enough on the road it won't achieve 20mpg, and on the average track you'll be lucky to reach double figures. Obviously touring consumption is another matter entirely, and so for that matter is endurance racing on circuits like the old La Sarthe - lots of long straights and fast bends. Cheers, Alec Quote Link to post Share on other sites
MadMarx Posted December 31, 2008 Report Share Posted December 31, 2008 If your lap speed is 83.5mph, or 133.6kph, that's 10mpg. If your lap speed is any slower, it's less than 10mpg. Hi Alec, I do 50 km in this 30 minutes. But I must confess this is race consumption. On normal Autobahn use with an average speed of 130 kph I need 11 L per 100 km. I don't know what that is in you measurement system. Cheers Chris Quote Link to post Share on other sites
Tom Fremont Posted December 31, 2008 Report Share Posted December 31, 2008 On normal Autobahn use with an average speed of 130 kph I need 11 L per 100 km.I don't know what that is in you measurement system. 21.4 miles/ US gal or 25.7 miles/ Imperial gal Quote Link to post Share on other sites
mandarawessels Posted December 31, 2008 Report Share Posted December 31, 2008 Hi Alec, I do 50 km in this 30 minutes. But I must confess this is race consumption. On normal Autobahn use with an average speed of 130 kph I need 11 L per 100 km. I don't know what that is in you measurement system. Cheers Chris that is 1 in 9 as they say in Europe: 1 ltr will give you 9 kilometres modern cars will do 1 in 18 or there-abouts! happy newyear everyone!!! cheers John. Quote Link to post Share on other sites
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