Major Stare
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| posted on 29/5/07 at 10:27 PM |
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What do you rev your X-Flow to ?
Never know what to rev limit my X-flow to?
I understand it varies from engine to engine.
1700 X-Flow
MegaSquirt with GBR600 injection
Head polished and ported
BCF2 Cam .387" LIFT/290deg duration
Jon "FISH"
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DavidM
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| posted on 29/5/07 at 11:06 PM |
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Mine is a standard 1300 crossflow. At the moment I don't take it past 5000 RPM because it's done less than 2000 miles since it was
rebuilt. Maximum power is at 5750 so there is no point revving it past that once it's properly run in.
I think the BCF2 cam produces maximum power at 6000 RPM, in which case there is not a lot of point revving yours past 6000, in my opinion.
David
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Fatgadget
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| posted on 30/5/07 at 12:36 AM |
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Had a 1640 with an A2 cam.Tuftrited crank and balanced with 125E conrods. Used to regularly rev it till the valves bounced  Rev counter
didn't work!
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Ham
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| posted on 30/5/07 at 06:53 AM |
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I've got a recall function on my rev counter, at the mo it shows a max of 7400!!!!
I've got my shift light set at 5800, so by the time I change it is revving at around 6500
1660,lightened and balanced 275 deg cam twin 40's - BTW
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02GF74
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| posted on 30/5/07 at 07:35 AM |
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... ooh, I posted soemthing similar a while back.
I have had mine to 7,000 ish I think
... but there is not point. You aim to rev up to around the point where you get max. power; thjat is determined by cam, engine internals, valve
srpings etc.
I found that at the high revs. I took it took there was a losss of power and unpleasant nois - valve bounce I reckon - whcih acts as a very primitive
rev limiter.
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David Jenkins
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| posted on 30/5/07 at 08:20 AM |
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I've set my shift light to 6100, rev limiter to 6300.
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britishtrident
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| posted on 30/5/07 at 11:07 AM |
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A high revs bore wear is the problem with xflos because of the (top) heavy pistons.
For competition use revving past peak power means that the revs when the next gear is selected will be higher up the torque curve.
The old Lotus TwinCam engines which had the old 1500 pre-xflo crank & rods were redlined at 6500 rpm, remove the rev limmiter and 7000 caused no
sweat.
So it really depends on the cam, valve gear and how much wear you want to risk.
[Edited on 30/5/07 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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ever88
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| posted on 31/5/07 at 01:13 PM |
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spent a fortune on my xflow before I let it go.
my top tip if you think it's worth it was to use the older hot cams that were heavy in duration and low in lift. this way I could fit my high
lift roller rocker and get the lift on such a cam and change the spec on engine with minimal efforts. for those guy's racing on track I'm
sure this would be very useful as changing gear ratio's etc is a lot harder. once you have two familiar tune positions you effectively gain
some performance at higher revs to make most out of a gear ratio.
my spec was to use the 1fr1 cam with standard rocker ratio of 1.52 to 1 or use a 1.69 to 1 higher rocker ratio. I did this as simply to experiment
with drive ability for road use. both choices were quite severe for road use.
food for thought!
cheers all
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thepest
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| posted on 1/6/07 at 07:21 PM |
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Max I used to use is 9000, using a kent 264 cam.It has alot of power with that cam but not very torquey below 4500.
To get to 9000 I used fiat flat-top pistons,lightened and balanced rods,vandervell racing bearings and a high pressure high capactiy oil pump.
However it is more important to be able to use the power where you need it:
Right now I am using an A2 cam, which revs to 6500 maybe 7000 max. And I am using a quaife close ratio box to remain within the powerband.
The A2 cam is much better at lower RPMs which helps coming out of corners quicker.
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smart51
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| posted on 1/6/07 at 07:55 PM |
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quote:
Originally posted by DavidM
Maximum power is at 5750 so there is no point revving it past that
Not so. Shifting from 1st to 2nd will drop the revs from 5750 to 3500 or 4000 - a big drop in engine output. 6000 or maybe more in 1st will keep the
revs up when shifting to 2nd, keeping the engine on the boil.
My engine produces peak power at 10,100 rpm. The It still pulls hard at 11500. The optimum shift point is more above peak power the bigger the gap
in gear ratios.
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