I have built a new motor for my bug and ran it on a Dyno Dynamics dyno this morning……only about 85hp at the wheels approx 6000rpm ( 135km/hr indicated by the dyno, top gear std ratio….unfortunately the dyno does not output power vs engine RPM)

My motor;
*2276cc, 82 x 94mm
*Engle FK10 cam, 1.4 ratios
*twin 48 dellortos (40mm chokes, 70 idles and 180 mains)
*044 heads, home wedge port, 42 x 37mm valves, 3 angle grind, opened up and cleared exhaust ports, CCd, unshrouded etc… CB tall manifolds match ported.
* A1 low down header 1 5/8”, custom 2.5” hideaway exhaust with straight thru magnaflow muffler
* comp ratio 9.3 :1
* straight cut cam gears
* 12lb flywheel
*5.4” scat I beams


The motor drives really well, the cam comes in strongly at about 3000 – 3500RPM and pulls well up to 6000RPM (I haven’t taken it further yet). The thing is, it feels very powerful??!!

The exhaust probe indicated I am leaning out at higher RPMs (up to about 17)

What do you think about the low hp reading?

Cheers

17:1 is scarey lean.
First make sure your fuel pump and lines are adequate to supply the system with enough volume.



Also, if that is correct you may have to reduce your air correction jet a bit. (or a lot!)
That main is borderline big depending on your altitude above sea level,
and so a large air may have been installed to compensate.
This in turn may cause your lean-ness up high.

CB always used to recommend a main size that is 4.2 times the size of the venturi. (and start with a 180 air corrector).
I would choose something in the 4x to 4.2x and then tune with the air corrector.

Most engines with cams like yours should be well above 100 hp if the heads are up to the job.

These are just rules of thumb, so details may vary.

Prolly should of tried to dyno it in 3rd.

I wonder about that too, a Vw in high gear may read a lower hp reading at the wheel because of the loss thru gearing. Most v8 cars are 1 to 1 ( TRANS )in high gear, if yours is .89 your readings should be off. I have never tried it ,but would be interesting to see if or how much differance it would make in third. Mike

you shouldnt be worring about the HP reading it will and does vary from machine to machine and day to day

the dyno is a stationary tuning tool for tuning the engine under load

sure they give a reading but its not really important

If you make any more changes to the engine take it back to the same place so you have a comparrision to use to see if you have made any improvements

As per Dave i would be worried about the 17 to 1 fuel reading you may burn a head very easy better to be slightly rich around 13 or so

thanks for the replies.

I am worried about the lean-out also. FYI, the motor is in an oval with stock fuel line (reserve tap removed). I have mounted a whopping big carter pump under the tank and a holley reg before the carbs. I have adjusted fuel pressure to 2.5psi. Dave, when you mentioned about making sure I am getting enough fuel into the engine....what volume / minute should I get out of the regulator (i.e. for the two carbs). Also, originally I had 3.0mm needle and seats for the float valves, which were leaking. I could only get 2.25 replacments - could this also be a cause of the hight RPM lean out.(maybe I ould drill them out??)

once again thanks for the help.

The stock fuel line was too small for my 1915. The heads showed signs of slight over-heating.

I replaced it with 8mm rubber fuel hose and the difference was AMAZING.

Not sure about pumping pressures and volumes, but the first thing I'd be doing is putting in large fuel hose.

yep CHANGE THE fuel line 4 SURE

minimum should be 8mm

the stock fuel line used to feed a 122 main in a 36Hp engine now your trying to feed 4 x 180 mains thats not on

I get the message - thanks. I will change to an 8mm steel line.

I figured that since the std 36hp pump was sucking fuel through the line this would be the limiting factor (cavitation etc...) So fitting a high pressure/ high volume carter pump under the tank, I figured I could simply just blast enough fuel through?? It sure seems to come through in a hurry.

Anyone have an idea of the required flow rate of fuel to the "T" piece?

I will check my flow rate before and after fitting the new line and let you know the difference.

Also, any feedback on the 225 float valves ?

Dude,

8mm line
2.5 needle valves
4-4.5 psi past the reg
make sure the needle valves don't leak with the engine off and the pump running.
try to run as much fuel pressure as you possibly can without problems.
Remember that pressure through a small line does not = volume and the bowl will still empty.
8mm lines as a minimum.

That engine should be well over 100hp mark, but don't stress because it might be the dyno.
Sometimes with the less powerful cars you need to ramp them in 3rd.

power is power is power. The only difference would be through different pumping losses and drag via the different gearsets. ie: Not much...

load changes and speed test is what changes that changes the power figure.

well I have just gone out and bought some 3/8" bore hydraulic tube....reckon this should flow ok (going from one extreme to the other!!).

I will measure flow rates out of the reg (set at the same pressure) for the stock set-up and with the ginormous steel fuel line for interest sake....will keep you guys posted.

another question - can I simply drill the orifice a larger diameter in the float valve seat. The way I see it, this will reduce the seat area and maybe cause me some grief.

Sonds like some good advice there.
I personally would have recommended 1/2" OD tube, and what you have chosen is it!

My tube car used 1.25" OD (31.75mm) stainless tube for the supply line...no such thing as over kill!!

Worst thing that can happen is your tank volume will effectively be enlarged.
Mine added 2 lt to my volume!


There are a few rules of thumb I use for methanol, but I would have to convert them over to petrol use,
but Nicks advice covers everything anyhow.

But I would not start drilling those deals out...keep things "off the shelf" where you can.

On the fuel pressure - 2.5 - 3 is all dells will hold in my experience. I spent hours with float levels and fuel pressure on my 48s.

Jetting is likely to be pretty square compared to idfs. I had 48 dells (non tri jet) on my 2276 and ended up with 175 mains and 180 airs, 65 idles. (K8 9.5:1). Tri jet dells will be closer to 200 airs

now the next question - anyone have any clever / neat ideas about how and where to run the steel fuel line. Being 1/2" OD i reckon it would be a pig to run down the tunnel. Under the car and I reckon it might pick up too much heat from the road over summer??

run your line inside the tunnel much safer just make sure you solid mount it inside and test for leaks dont do what the hippies do and run it loose under the pan. Dave 2322mm long fuel line?

Ive seen line run through the tunnel, heater channel, and the lip between pan and sill on the outside (stainless would be best).
I ran a 3/8 steel line through the tunnel with the body on. Prick of a job but doable. Cut an access hole in the tunnel in front of the pedals and it makes it easier. I managed to secure it in the rear through the gear linkage access and at the front through the access I cut. Used some 3/8 rubber hose split and fed that over the steel line to stop any annoying rattles.

I did mine like this! It is bundy tubing and is - 6. As above I have also slipped rubber hose over the top to stop rattling.





T54

I have a file from a few guys both here and in the states showing how to do the procedure.

shoot me your email address and I'll send it to you.

regards Craig

Out of interest (sorry to get off track), has anyone done back to back dyno comparisons keeping all variables the same (engine combo/jetting/etc etc) to determine the difference in RWHP figures?

I hear a lot about the variations in dyno figures which I am sure is true, but haven't heard of the variation in actual figures to date - would be really interested to hear from you guys with more experience than me!

sorry to hijack deluxe hunter - thought it could be relevant to the thread though.
Alan

I cant say I have any experience with Dyno's, though I do remember reading in a ZOOM mag once, where they did a comparison on a fair few Dyno's and there was quite a varience accross the different ones. It pretty much said some will read High some Low... If tuning it pretty much said always go back to the same one...

But I guess if you use the same Dyno all the time for your tuning this is the best, I guess they are tool rather then giving the exact power. I have heard some ricers will go to one dyno just to get a big hp readout...

At least Dyno shootouts are only ever done on the one dyno...

I guess its a liitle black art, Like VW's

The Dyno run aretoo expensive to go back to back for data purposes

old speedway modified 458 hp at 5800rpm two weeks later 428hp same revs same sorta day was 10 years ago thou and am streching the memory on the facts but was with a top engine builder on the gold coast and he had no answers for us only answer we could cum up with was dyno differences it was a eddy brake chassis dyno if anyone cares!

About 2 years ago I went to Custom Bugs and Busses and then a guy on the central coast. I think both machines were dyno dynamics. There was only a 88 to 89 horsepower variance and that could be due to a slight change in ingnition timing.

Before and after that I'd used Silverwater Automotive Service and their readings seemed right. In the early days I started with 76hp with some badly shrouded big valves. Then in the last year or so I got 96hp due to better flowing heads and a bit more cam duration with the same CR. Then 99 thanks to a 3 angle valve job and a bit more timing.

Using the Warwick Weekend 2006 vs 2007 to verify the 3 extra horsepower and perhaps another 1.5 from a power pulley, it was good for another 2mph (70mph vs 72mph)and 2 tenths over the 1/8th (9.7 vs 9.5).

God I crap on some times.

CT