honda cbr600 engine for a formula student car intake was my final year uni project and came up with a interchangeable manifold: - bolt on extra rows of runner length - bolt on 3 different size plenums - vary injector position (nearer / further from ports etc - all sealed with o-rings (as seen in pic) - trumpets inside plenum
its summed up in the graphs further up the page kinda but basically to keep things simple , everything was done in threes 3 runner lengths (made up of 70mm sections that bolt on), one row of 70mm sections were a bit fancy so that they accepted injectors at 45 degrees, sitting in recesses so they dont intrude into the path of airflow (see pic up above, lookin down the port) 3 plenum volumes, small 85mm dia x350mm long , medium 110mm dia x350mm long, and huge 135mm dia x350mm long (cant remember sizes exactly.. im at work .. the files and such are on home pc) all plenums had bellmouths / trumpets on the inside, which added about 50mm to the length of each setup every setup featured the "port adaptors", which are 45mm long sections that allow the head to have the intake system mounted on changing the runner/primary length makes the biggest difference to torque / power curves -short runners 70mm (+45 +50) gave a flat torque curve that didn't really start to drop off till 11k rpm which results in high bhp so long as the revs are kept really high -medium 140mm (+45 +50) brought the peak torque value down the rev range by 1000 rpm ish .. and bumped the peak torque figure up considerably, after this the torque dies off .. and you are left with a lower effective rev range than with short runners. -long runners 210mm (+45 +50) bring the peak torque value further down the rev range again .... giving an even lower useful rev range .. so high torque at lower rpm (peak value is at 1000 ish rpm lower than with medium runner length so changing runner length alters whereabouts the torque peak occurs on the rev range you can see how putting short length throttle bodies on a engine that only revs to 7k rpm can leave people dissapointed. plenum volume -small volume = wider effective power/torque band, lower peak values -medium vol = reduced effective band, increased values -large vol = narrow effective power band, maximum torque/ power ^ this is what happened when we ran lots of engine dyno tests anyway oh and throttle response seemed unaffected by the massive plenum
the system was dyno tested a reasonable number of times only testing it had in the car was a few laps of the car park our car was fairly heavy for a formula student car yet our sprint time, which featured a driver who had never sat in the car before, was really good (not best but beat a lot of fancy vehicles) so if that setup could propel a complete novice in a heavy car to a good time ... i consider that proven
car 39 The University of Huddersfield 4.316 was the time .. and remember that the driver sat in the car having never been in before and only had 2 runs due to not having enough time for the full 4 runs http://www.formulastudent.com/2007event/2007Results.htm all .pdfs with results are on there.... finished the endurance .. eventually but I think it was too slow to be scored due to an electrical fault
Cool, what I ment was what trumpet length and plenun did you run with on the day? and what Rpm were you rveing to? cheers Tom.
oh lol well my dumbass welsh buddy doing the rear suspension .. overestimated how much space would be available under the braces so had option of run with: 140mm and small plenum 70mm and small plenum 70mm and medium plenum 70mm and large plenum went for the latter ... as it produces the highest output i didnt drive ... we had a guy who has had lots of race experience with locost series and an absolute tool who said he could drive but ended up being terrible plus 2 other normal guys who got a drive on lesser events *note* Formula student does not allow individual throttle bodies ... you have to use a single with a 20mm restrictor i told the guy on the sprint event not to change up till 13k lol good old bike engines! i havent actually got the graphs from the large plenum tests .. as we did those after project hand in i think its been re-tested this year ... i will enquire!!
Intake design looks very good mate! I'm designing the front suspension for my uni's Formula Student car. So i might want to pick your brains at some point if thats ok? What sort of power was your engine making? Sean
around 95bhp though not entirely sure matey as our dyno was calibrated quite a bit out and read high all i know is that the figures my best setup generated were near double what the setup from year before produced as for front suspension we had ........... 5 link floating kingpin crap one of our lecturers insisted that the steering rack was infront of the drivers feet so that it was MSA compliant..... which messed up our competitiveness you need a nice short car to get round the track if an FS car is to do good it needs to be totally reliable, totally rule compliant to get through scrutineering as early as possible so that you can get through all the tests build a car that the design judges will love rather than trying to be radical and cutting-edge i'll help however i can matey, as I woulda liked some advice from someone who has been there done that. Whats your cars current spec looking like mate?
On the original topic again. Dave Walker has written a few magazine articles on tuning trumpet lengths, turns out that having unequal length trumpets can iron out flat spots. I think most of the articles were in Circuit Driver Brunty
unequal lengths would mean that the cylinders are tuned to different engine speeds it could do as suggested above but it sounds like having a tandem bicycle with one guy kaining it and the other putting in mild effort ... more rewarding when all working together i'd imagine but hes done the research on it so he's probably right
This is why I have always used DCOE's, the body length is a lot longer than most TB set ups. Although, that can present its own issues on 8v's when the trumpets are close to the bulkhead.
I saw a Hillclimb BMW once that had got manually operated variable trumpet length. It was a cable operated slip joint....basically his local hillclimb circuit was mainly fast bits with one slow corner and he was struggling to get the car to pull out of it so he came up with this idea. I think it was a Mini choke cable so he could pull the cable and lock it into position by turning it.
Beating a dead thread yes but just out of curiosity is there anything to suggest you can have trumpets that are too long? I managed to squeeze 45mm I think on my DHLA's in an 8v but it's been suggested that by cutting down 5 or 10 mm on the front engine mount (one of Duff's works) and tilting the engine forwards I could buy more room back there. Have run this by him and in principle should be okay especially as the car's not particularly low I wouldn't have to worry about the sump. The big problems would be oil filter hitting, driveshafts and exhaust manifold as it's all stainless but I can't imagine I'd need to drop the engine that low to gain another 20mm, especially as it would tilt the carbs further upwards. I would like to fit 60mm on if possible. Also, has anyone tried these special "radiused" trumpets that are meant to be better than standard ones and have anything to say about them?
