Edlebrock Carb

Pat Calhoun · Posted: Thu Oct 04, 2001 3:08 pm Post subject: Edlebrock Carb

What happened to the new edelbrock 125 carb
And does anyone have experience with these?

John Denman · Posted: Thu Oct 04, 2001 3:15 pm Post subject: Edlebrock Carb

I have the 38X34 model and have done some testing so far with it. It works pretty well and adds about 300 RPM to the bottom end when compared to a PWM at 39.2MM. It is a little tricky to set up at first if your used to something like a Kiehn.

I am waiting on a 42X38 prototype.

So far it shows promise on short tracks at NTK it dropped my time by .3 seconds over the PWM with the same EGT and plug color.

Andy Szyszkowski · Joined: 01 Aug 2001 Posts: 149

quote:
Originally posted by John Denman:
I have the 38X34 model and have done some testing so far with it. It works pretty well and adds about 300 RPM to the bottom end when compared to a PWM at 39.2MM. It is a little tricky to set up at first if your used to something like a Kiehn.

I am waiting on a 42X38 prototype.

So far it shows promise on short tracks at NTK it dropped my time by .3 seconds over the PWM with the same EGT and plug color.

John,

I have not seen the carb. Only pictures and conversations with Edelbrock is as close as I've come so far. From the outside, I would suspect the performance you've witnessed is likely due to the smaller venturi as compared against your PWM 39.2. Smaller carbs usually atomized better, and provide increased circuit response due to the higher velocity from it's resultant smaller size. Perhaps if you compared any of the smaller carbs against your 39.2, you may witness a similar result. At least those have been my experiences......FWIW.

Andy

John Denman · Posted: Thu Oct 04, 2001 6:57 pm Post subject: Edlebrock Carb

Andy you are correct. We had planned to dyno test it earlier, but it arrived beyond the window we had open for 125 development this summer. We will have better data available after the Red River Regional season winds down.

John Denman · Posted: Fri Oct 05, 2001 2:21 pm Post subject: Edlebrock Carb

I contacted Edelbrock and they are waiting on getting a motor for testing before they continue development on a larger carb. Expecting sometime in early Deecmber now.

They also provided a carb to Dominique Claessons for 80Jr, but have not heard back from them. Does anyone know if Claessons has been running a strange looking carb? Especially at Norman!

Please respond if you have any information about Dom's carb at events.......

Rick, Mark?

Bill Martin · Posted: Fri Oct 05, 2001 6:48 pm Post subject: Edlebrock Carb

quote:
Originally posted by John Denman:
I contacted Edelbrock and they are waiting on getting a motor for testing before they continue development on a larger carb. Expecting sometime in early Deecmber now.

Rick, Mark?

John,
Little digression from this, but I'm curious if you have any idea why Edelbrock did the oval bore on those carbs. Seems like extra skin friction compared to an equivalent area round bore. Should be good for P.O.'ing the tech inspection guys though!

Rick Blood · Posted: Fri Oct 05, 2001 8:22 pm Post subject: Edlebrock Carb

John,
Tanya knows Cammy Edelbrock and had inquired about a 28.5 several months ago.
I'll have her check again Monday.
Mark on the other hand has had some interesting results from the Kehien carb.

John Denman · Posted: Sat Oct 06, 2001 6:03 am Post subject: Edlebrock Carb

quote:
Originally posted by Bill Martin:

John,
Little digression from this, but I'm curious if you have any idea why Edelbrock did the oval bore on those carbs.

Edelbrock says its to keep the velocity up under part trhottle. You would think that slide at part throttle would do this right? But it may be the effect of velocity across the jet thats crucial and an oval bore would appear to affect the flow around the jet.

Andy Szyszkowski · Joined: 01 Aug 2001 Posts: 149

quote:
Originally posted by Bill Martin:

John,
Little digression from this, but I'm curious if you have any idea why Edelbrock did the oval bore on those carbs. Seems like extra skin friction compared to an equivalent area round bore. Should be good for P.O.'ing the tech inspection guys though!

Bill,

Though there are other oval bore carbs available, this is predominantly done to provide a strong signal to the transitional circuit(s) when the throttle slide opens. It helps to alleviate the bog so predominant in larger (for the application) carbs. As an example, if all things were equal, a 39mm oval bore carb would probably yeild better throttle response than a 39mm round bore carb.

There are other ways to design to improve throttle response, but the oval bore is probably the simplest and arguably the most effective. One of the carbs I designed and built, had a "double D" shaped (no jokes please!) bore that was layed flat in an attempt to more closely replicate the opening in the reed cage. Wth it's transition circuit design, the throttle response was very good, even though there was this sudden large area of exposure when the slide was opened. So, it is possible, but it must be designed-in from the start.

You're right, the tech guys don't like the oval stuff.

Andy

John Denman · Posted: Mon Oct 29, 2001 10:41 am Post subject: Edlebrock Carb

A bit of an update on the Edelbrock Qwiksilver carb

Different motors configurations seem to show the same results of improved bottom end response, but varied a little on top end response. Using a Kiehn PWM in 38 and 39.2 mm bore with a 99 OEM ignition, we found the Edelbrock 34x36 added about 200 RPM to the bottom over the 38, and matched the top end RPM at 12,500 for our motor with overrev to 12,800.

Its very drivable compared to either of the Kiehn carbs. That doesn't show up with dyno testing.

We ran it at the Motorsport Ranch Road Race recently and it did not loose much, if any, top end as we were expecting it would. The drivability enabled much smoother turn exits and launched very well out of turns.

It did suffer a slight bog in one long turn that also had an effect on our 80cc with a pumparound system. Rather than drop 2 gears on the turn, it managed to pull well enough with only a single gear drop and no bog.

The overbore carb is still being worked to make it as crisp and responsive as the std bore carb.

Testing with a PI showed a drop in top end power over the curve for the 39.2 mm carb. More work to do here in curve profiles.

EGT remained very stable at varying air temps without need for adjustment, while the 80 went two jet sizes smaller from AM to noon to keep EGT on target.

More updates to follow as we do some curve massaging and get the overbored carb working to our satisfaction.

Andy Szyszkowski · Joined: 01 Aug 2001 Posts: 149

John,

I was denied direct e-mail access to you, so I'll post here. If interested, you can e-mail me.

quote:
Originally posted by John Denman:
A bit of an update on the Edelbrock Qwiksilver carb

Different motors configurations seem to show the same results of improved bottom end response, but varied a little on top end response. Using a Kiehn PWM in 38 and 39.2 mm bore with a 99 OEM ignition, we found the Edelbrock 34x36 added about 200 RPM to the bottom over the 38, and matched the top end RPM at 12,500 for our motor with overrev to 12,800.
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John, do I understand correctly that you are finding improved dyno results with the Quicksilver over the Kehin?
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Its very drivable compared to either of the Kiehn carbs. That doesn't show up with dyno testing.
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I am not surprised to hear this. As I speculated in an earlier post, the smaller carb would produce this result. On my roadrace CR125, I run a 35mm flat slide pumper with very satisfying results.

We ran it at the Motorsport Ranch Road Race recently and it did not loose much, if any, top end as we were expecting it would. The drivability enabled much smoother turn exits and launched very well out of turns.
**********
What did the stopwatch show? Were you able to do a side by side comparison?
**********
It did suffer a slight bog in one long turn that also had an effect on our 80cc with a pumparound system. Rather than drop 2 gears on the turn, it managed to pull well enough with only a single gear drop and no bog.
*********
Did you use the traditional Mikuni dual outlet pump with one line bypassing? If you continue to experience a bog on long sweeping turns, I have a possible solution.
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The overbore carb is still being worked to make it as crisp and responsive as the std bore carb.

Testing with a PI showed a drop in top end power over the curve for the 39.2 mm carb. More work to do here in curve profile.
**********
What are you trying to gain with the larger carb if the dyno didn't give the nod to the 39.2? Once you start going beyond the size threshold, a float carb really struggles with attempting to carburet effectively. I would perhaps try playing around with the shape of the throttle bore to gain some of that crispness your looking for.
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EGT remained very stable at varying air temps without need for adjustment, while the 80 went two jet sizes smaller from AM to noon to keep EGT on target.

More updates to follow as we do some curve massaging and get the overbored carb working to our satisfaction.

*********
Thanks for keeping us posted on some interesting and well thought-out testing.

Andy