i was wondering about the stage 3 cam for our car's they say it's for carb motor's only, Is it a vaccum reason? then if so how do dragster's run car's with such high lobbed cam with no problem's?
i was wondering about the stage 3 cam for our car's they say it's for carb motor's only, Is it a vaccum reason? then if so how do dragster's run car's with such high lobbed cam with no problem's?
its easier to tune the carb, and you might have to bump your idle speed up alittle to make it idle.
Stage 3 (or any high duration cams) have a lot of overlap between the intake and exhaust valves at the end of the exhaust stroke. This means that for a short while both are open at the same time. This is good at high RPMs because it uses the suction created by the exhaust to help draw in more air/fuel charge from the intake. However, at low RPMs there isn't as much suction created by the exhaust so instead of sucking in more air/fuel, the exhaust gasses tend to back up into the intake. This creates a really lumpy vacuum signal which confuses OEM type fuel injections that use intake manifold pressure (MAP) to determine engine load and therefore fueling. To use fuel injection with a really hot cam you need to use something else to determine engine load. Usually this is the throttle position. It's not as accurate as MAP but it gets around the lumpy vacuum signal.
Carbs have an easier time with lumpy vacuum signals because they meter the fuel continuously in an analog fashion (variable flow) based on manifold vacuum, instead of time based (injector pulse width) like fuel injection does.
C|
so the MAP sensor is what i have to change? then i would have to upgrade my ECU to run such a hot cam as well right?
Now your talking OBD-1 conversion. Theres no ecu that's a plug and play for our cars.Originally Posted by JohnBoy
I can't read the signature rules so MrBen deleted my signature.
so what type of MAP sensor could i use or could it be done with the OBD-1 conversion?
alright guys i just talked to my dad and he explaned why it wouldn't work but thank's for the info
It's not the sensor but the ECU itself. The MAP sensor will still work correctly but the ECU won't know how to interpret what the MAP sesor is telling it. I don't know much about Honda ECUs but I thought some of them (OBD1) could be reprogrammed to do TPS based fueling instead of MAP based. But I could be wrong.
C|
so then the obd1 is from early 90 honda's? or is there a better aftermarket one
has anyone hear used the stage three cam? torque any good at lower rpm? stage 2 is probably better
Remember when Openloop did that dyno test? He put in a crazy race cam and then put in a 272ish cam. I don't know if he did any kind of tuning between, but he lost horsepower and tons of torque with the race cam. I'm guessing because he didn't want to rev the motor to where the cam actually starts to make power. My guess is that most "stage 3" cams (290ish duration?) are designed for the motor to be spinning up around 8500-9000RPMs and will make their power up that high. Unless you're building a serious race motor, you probably don't want a stage 3 cam.
thats what i was thinking, wasn't sure of the powerband
but if your drag racing a fwd car the bottem end is were the torq is and if you can't hook up then your sol. so the top end is a little more important. so fat tires and a wheel, stiff rear end and a wheel bar would be you best friend
The stage 3 cam is really for the most aggressive NA build and our build really wasn't that aggressive. With compression around 10.5:1 the overlap provided by the cam is too much. Your going to need 11:1+ compression with a cam this aggressive. Probably need some larger valves as well. As with any change in air flow characteristics tuning is needed but just wasn't feasible at the time. Only tuning done was cam timing and fuel pressure. Building engines really comes down to piecing parts that work well together and its not that a stage 3 cam is bad, its just you need all the other supporting parts to get the best results. If you look at the graphs its obvious the potential is there as power is still good up top as the engine really opens up at 7K but just need that extra compression for the added kick.
https://www.3geez.com/forum/showthread.php?t=57136
remember a drag car is not always a street car. there are some give aways for performance like not being able to use power brakes etc because of the low vacuum that larger cams make esp at idle.
Also most drag cars run an auto trans that has alot of slip built into the torque converter so the motor will be freed up at low RPMS and slip a little at launch to get into the power band of the motor sooner.
Most guys can't really run over a 3000 rpm stall convertor on the street.
Larger cams do "bleed" off compression at idle as well so higher compression motors can be run that you could not run with a stock cam.
Really with our cars a cam swap is pretty easy so hell if you got a little money try it.
wp
1988 Lxi owner since August 1995
336k miles running strong!
Now running E85.
Oldblueaccord <<< MY YOUTUBE PAGE!
Hey Mike, do you have any more detailed specs on that 256/270 cam? Would you happen to know the duration at 0.05" lift?
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Sorry don't have any specs handy.
if your going to uprgrade your cam to a delta 272 does ur car have to be mani?
all cars have manifolds. so you either got a carb mani or fi mani.
i think he ment if it has to be a manual....i dont think so...your trans wont like the high rpms
1989 Honda Accord LX-i
B18c1 swap since 7/2011
175whp and 132tq
Redzone tuned
otay, ya that looks to be a little more under standable. lol
yea, ive got a delta 272 and a webber. and my car is automatic...
for now. lol.
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