Martin Plant Posted July 19, 2004 Share Posted July 19, 2004 I have a Blackbird engined 7 with a tuned lump that makes about 190bhp. It runs carbs (Keihin flat slides). The car won't rev out which could be due to air flow but I think its much more likely to be due to poor fuel flow. That's because if I back off the gas (letting the floats fill back up) then gas it again it will rev out. Currently the car has a Facet red top pump and a petrol king regulator. I've wound the regulator screw right in and can't get more than about 5psi. I'm tempted to whip the whole lot out and replace it with a fuel pump that can deliver a high flow rate at low pressure. Someone has recommended a Fireblade pump, but that was designed for a 130bhp engine so I'd be concerned whether it too could deliver enough flow. I'd appreciate your advice, especially if anyone else has solved the same problem. Thanks Martin www.caterhamblackbird.com Link to comment Share on other sites More sharing options...
barry.h Posted July 19, 2004 Share Posted July 19, 2004 Martin, I understood the problem was usually too much fuel from a standard pump resulting in flooding as the float chambers overfilled. Certainly my regulator is on its lowest setting and the pump only produces about 5 psi. Anyway the Petrol King regulator range is 1.5 - 5 psi. In terms of high flow rate the facet should be ok at 35 gals/hour. I don't know what the Fireblade flow rate is though. Probably not much help but I'd certainly be interested to learn how you get on if you go down this route. Barry Link to comment Share on other sites More sharing options...
Martin Plant Posted July 19, 2004 Author Share Posted July 19, 2004 I'm not an expert by any means, but my understanding of the problem is that you have to wind down the pressure using the regulator to avoid overcoming the needle valves (as you mention). When you do that the flow reduces to a trickle. So what's needed is a pump that can deliver a high flow rate but at low pressure. Apparently the blade pump can do this. I'm sure a fluid dynamics expert will pop up any moment and say I'm talking b*ll*x mind. Anyway a friend is going to lend me a 'blade pump to try. Thanks. Martin www.caterhamblackbird.com Link to comment Share on other sites More sharing options...
barry.h Posted July 19, 2004 Share Posted July 19, 2004 Mmm interesting. Presumably this is to mirror a gravity feed? Anyway I'd be interested to learn how you get on. Cheers, Barry Link to comment Share on other sites More sharing options...
MikeSA Posted July 19, 2004 Share Posted July 19, 2004 Hi Martin I thought you were the teacher in this classroom You may recall the problems I had getting my setup to work originally. Mine is now more or less a replica of yours with the Petrol/filter King, I have the original pump feeding the Petrol King with the excess pressure on the return line, but I am not having trouble at high Rpm. In fact I am only running about 2.5psi, any more tends to flood at low Rpm. I assume there is some compensation for altitude but it still doesn't stack up to your numbers. My car is making 200bhp so power isn't a problem. The only difference is I have the original carbs and cams and my main jet size is 175 for what thats worth. What rpm are you trying to take the car too 😬 Hey, I just drive em - fast! Link to comment Share on other sites More sharing options...
Morls Posted July 23, 2004 Share Posted July 23, 2004 I'm using a CBR600 pump on a fireblade motor in mavis and it seems fine. It's also simple, light, reliable and cheap. On big bike pumps in general, I've not heard of TT racers changing them on big proddy bikes, and they're often flat out for a long time, so thery may be capable of a factor of over delivery. As they're rarely damaged in crashes, I would imagine most of the breakers in MCN (on Wednesdays) would have a hi-flowing pump off any of the big 1000/1100/1200/1300 bikes for cheap money. If they were cheap enough you could try a 'time to fill a bucket' flow rate test for comparison? Mark Look it's Mavis here and Jubilee 7 here Link to comment Share on other sites More sharing options...
Martin Plant Posted July 23, 2004 Author Share Posted July 23, 2004 I've got a blade pump and some new hose that I am going to try fitting in the next few days in Germany, will let you know how I get on when back from the 'ring Martin www.caterhamblackbird.com Link to comment Share on other sites More sharing options...
barry.h Posted September 20, 2004 Share Posted September 20, 2004 Hi Martin, How did you get on with the Blade pump? I ask because my Keihin carbed engine kept fluffing yesterday at Loton as I went left after a flat out run up the hill. I suspect fuel delivery mostly because I have run out of other ideas. I am coming round to your idea of too much pressure/not enough flow. Your thoughts would be much appreciated. Barry Link to comment Share on other sites More sharing options...
MikeSA Posted September 20, 2004 Share Posted September 20, 2004 Hi Barry I would also be interested in Martins reply, I am beginning to think there is no easy solution for the carb's (injection may be the only solution) if you are making big power. I am finding my car also struggles on the tigher shorter tracks where the G's are high whereas it is better on the bigger tracks with longer straights. Interestingly I also have most problems on a long left up a hill on one particular track I visit often. Is it possible that the whole design is just not up to it in a 4 wheel application. Link to comment Share on other sites More sharing options...
barry.h Posted September 20, 2004 Share Posted September 20, 2004 Hi Mike, That's interesting. As I recall you are on the original carbs but with a pump and regulator. If nothing else it does start to reduce my concern that the Keihin carbs could be the cause. FWIW I was able to reduce the problem in my last run yesterday by continually blipping the throttle as I braked and turned. It still fluffed but not as badly which led me to suspect that the problem lay in too much fuel not too little (the blipping helping to reduce the flooding maybe). Let's hope Martin has had some success. Barry Link to comment Share on other sites More sharing options...
Foxy Smith Posted September 20, 2004 Share Posted September 20, 2004 Guys have you had a look at Patrick Burns tuning manual for Keihin FCRs look at http://www.factorypro.com/tech/carbkei.html he gives figures for recomended float valve size on a HP per cylinder basis and recommends not ecxeeding the 2.4mm valve if running a pump. Recommended max pressure is 3psi. I think reading between the lines and also having had a look at the floats I think they would very easily be overcome by excess pressure resulting in flooding. This would surely be a problem a t low rpm/idle and not at the top end. He also talks about float height being critical and cause of many problems and makes reference to some kind of "sighting instrument" to check fuel levels in the bowls whilst the carbs are installed and seeing pressure from the fuel pump. Anyone know anything about this?? Link to comment Share on other sites More sharing options...
barry.h Posted September 20, 2004 Share Posted September 20, 2004 Foxy, Thanks for the reference, I'll have a look and see if I can understand it. I don't know whether it will apply to Mike as well if he is not on Keihins - the theory may hold good. I agree that it would be most likely to apply at idle - but in a sense is that what is happening when one backs off suddenly from a high revs/high power situation? Anyway, food for thought. Barry Link to comment Share on other sites More sharing options...
MikeSA Posted September 20, 2004 Share Posted September 20, 2004 Yes Barry I have the originals, which most of the time seem ok, but are not perfect. I run about 2.2 psi on the fuel pressure guage which is mounted on the regulator, some adjustment would be needed to this for comparison as I am at altitude. Any more pressure than this tends to flood at low rpm. Thanks Foxy, I will have a look too. The point about the float heights got me thinking, would the angle of the motor have any effect and the fact that it is mounted at 90% to the bike setup for cornering and acceleration? My motor leans over to the left quite sharply and the carbs don't sit flat with the line of the chassis, I would have to modify the intake hoses to get the carbs on the same line. Link to comment Share on other sites More sharing options...
ChrisG Posted September 20, 2004 Share Posted September 20, 2004 Regulators strangling flow at the low pressures that BEC carbs need is a fairly well known phenomenon, and the use of normal bike pumps seem to cure it in most instances. I think you'll find that its virtually one-pump-fits-all in the bike world so if a single blade type pump won't suffice could you not link two up in parallel maybe? Oh and yep, the engine should sit at the same angle as it does in the bike, running them at an angle would potentially affect the carbs although to what extent at the angle you have them mounted Im not sure. It could also affect the way the oil is picking up in the sump so really the base of the engine should be horizontal to the floor, as it would be on the bike. Chris Edited by - ChrisG on 20 Sep 2004 16:14:48 Link to comment Share on other sites More sharing options...
barry.h Posted September 20, 2004 Share Posted September 20, 2004 Thanks Chris. Bike pump it is then. Cheers, Barry Link to comment Share on other sites More sharing options...
Martin Plant Posted September 20, 2004 Author Share Posted September 20, 2004 I didn't get around to fitting the bike pump to mine on the ring trip for two reasons (1) I had an out-of-true ACB10 which meant the car wasn't much fun at full throttle and (2) it lunched 3rd/4th gear again which means the engine has to come out. I've decided to go back to the standard lump so will either do the fuel pump thing then or see how I get on with the regulator setup and a less fuel thirsty engine. Should have it sorted in time for Silverstone but am paying someone to do the swap for me this time. Am bored of working on the thing. M. Martin Link to comment Share on other sites More sharing options...
MikeSA Posted September 21, 2004 Share Posted September 21, 2004 Martin sorry to here about your endless niggles, partlicularly the gears. I must admit my car ran a lot better on the std engine with the regulator set up, than now on the stroked motor, but if you get tired of the FCRs let me know You need to come out to SA in November with your car, you can join me at Phakisa Freeway (one of this years GP Bike tracks) for a whole weekend of unlimited track time. Oh and in your money the whole weekend including hotel, food and the track is 200 pounds 😬 That would surely make you feel better. Link to comment Share on other sites More sharing options...
barry.h Posted September 22, 2004 Share Posted September 22, 2004 That's bad luck Martin. Hope you get it sorted OK. I think I shall give the Fireblade pump a go and see what happens. Got to do something. Barry Link to comment Share on other sites More sharing options...
Paul Thompson Posted September 22, 2004 Share Posted September 22, 2004 FWIW I run a cheapo electic pump from the local factors with the pressure reduced to 1 to 1.5 lbs on my Fireblade with carbs with no problems Link to comment Share on other sites More sharing options...
barry.h Posted September 27, 2004 Share Posted September 27, 2004 OK guys. I fitted a secondhand Honda 750 pump on Friday and sprinted at Curborough on Sunday. Did a time 0.6 secs under last year's class record so on that test at least it seems to work. It probably needs a stiffer test or a track day to prove it conclusively but it seems to be looking good. Interestingly, unlike the car pump/regulator setup, when the float chambers are full the bike pump stops pumping. In the same situation, even with the regulator at its minimum, the car pump was still pumping. Also I noticed that the car starts better from cold with the bike pump Barry Link to comment Share on other sites More sharing options...
Badger Bill Posted September 28, 2004 Share Posted September 28, 2004 I ran an African Twin pump on my 'Blade. No problems, either low down or revving out. 150sobs new from a dealer though... Lasted about 14k miles until it shook itself to death. BB Link to comment Share on other sites More sharing options...
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