Empi vs Weber-dyno comparison

[So Cal Mark]

Check out this video of a dyno comparison of Empi vs Weber IDF carbs. Also there is an installation and tuning guide for IDFs available


http://www.youtube.com/user/EMPIHPMX#p/u/0/WP3fOWaaQy4

[coise]

Thanks Mark,
This is really interresting, I was thinkimg about changing my 34 ADF for a double 40 IDF next year. I guess the EMPI will have to be the ones...

[azruss]

fun video. a 2hp improvement over 123 hp is only 1.6% improvement and they were using their own intake and exhaust. be interesting to see if the results translate to another type of engine with different intake and exhaust. The thing the dyno doesnt tell you is how the carb performs at less than full throttle. street tractability, etc. how does it compare to a weber in cost? does look like a nice carb.

[azygoustoyou]

They are about half of what the weber costs.

[TronDD]

The thing the dyno doesnt tell you is how the carb performs at less than full throttle. street tractability, etc. how does it compare to a weber in cost? does look like a nice carb.

Yeah, I think it would be obvious that a carb that has had improvements to air flow would make more horse power. But with both carbs jetted identically, one of them was either rich or lean and not optimised. Properly tuned, the carb with "less flow" could be making better torque.

Tim.

[So Cal Mark]

If you look at the dyno chart, you will see a dip in the torque curve of the Weber. That will translate as a sag in acceleration which is pretty typical of the off-idle stumble that Webers have.

[Raze]

I think this thread needs a healthy dose of skepticism. One set of pulls on VW motors comparing a Weber to a Chinese copy EMPI doesn't reveal much. I'd like to hear someone who's run one and had it stand up to normal use and abuse. Weber has a proven track record, just my .02. On the flip side, maybe Weber should start offering IDFs for 1/2 the price,

[sptcoupe]

I agree that a three dyno pulls doesn't show much, especially given how relatively small the difference is. I have seen that much change in output from one run to the next on the same motor, and even more going from a cool morning to a warm afternoon on the same dyno, so this small sampling in the comparo isn't significant.

My issue with EMPIs has always been with the quality of the materials used. Even the material in the screws that hold the carb tops on is worse (very soft), let alone the material used in the floats and the float holders, etc. I have had brand new EMPIs where I 1): couldn't screw the idle mixture screws in all the way (literally made the carb untunable), 2): was unable to get the throttle plates properly aligned (turned out the screw holes were not aligned), 3): had to replace the float mechanism with one from a cannibalized Weber because the metal material was so soft it kept bending and the float would hang up in the bowl, and 4): couldn't seat the bleed back valve because the thread wasn't deep enough in the holder to allow it to be seated.

But they sell a lot of them, and many are used in racing applications, so they maybe they have improved their quality from when I tried using them (and gave up) about 10 years ago.

[So Cal Mark]

If you're comparing the Empis of 10 years ago to todays' carbs your arguments aren't valid. Empi is licensed to build Webers, and they do offer them also. I've been putting Empis on for over two years and I've been quite satisfied with them. Empi went into the dyno comparison to prove their version flowed just as well as a Weber. If you want to spend almost twice the money for a big W on the side, I say go for it.

[sptcoupe]

I agree if they have improved them, and my experience is indeed from more 10 years ago. LIke I said, there are a lot of them on VW and porsche SCCA race cars and they seem to have a good rep. To be honest, I had never heard they didn't flow as well as a Weber. When did that debate start, and what was the basis of that claim? Maybe it was a bad experiences from early versions. The one I had where the throttle plate screws were mis-aligned certainly didn't flow very well, but with those kinds of issues cleaned up, they should be exactly the same.

One positive outcome of EMPI coming onto the market is the availability of various jet sizes. You can get about any jet size you need now, where as before EMPI, for many years, it was hard to find anything other than the usual 50s, 55s etc. I was just able to order 52s, 57s, and 142s for my 44IDFs - and they were all in stock! The guy at Pierce said it was because of EMPI making the IDF more affordable and attracting folks to a dual carb alternative. Good on em!

[timinator]

I think this thread needs a healthy dose of skepticism. One set of pulls on VW motors comparing a Weber to a Chinese copy EMPI doesn't reveal much. I'd like to hear someone who's run one and had it stand up to normal use and abuse. Weber has a proven track record, just my .02. On the flip side, maybe Weber should start offering IDFs for 1/2 the price,

Just thought you might like to know that Weber doesn't make carbs anymore. Since the big strike they had some years back they stopped producing carbs. The strike lasted for something like two years, so Weber started licensing companies to manufacture their carbs. Weber only makes components for fuel injection. EMPI just wanted to show their carbs performs like the origional Weber. EMPI also saw a fit to make a couple refinements that add to a smoother torque curve.
Doesn't really make any difference what engines they pick to make a comparison test with since all engines are just air pumps. I did like the idea that they choose a low performance and a moderate performance engine so customers could relate to what tuning is required.

[manoa matt]

It does not sound like a direct comparison. Right off the bat, they claim to make improvements to the flow and profiled throttle shafts.

There are even major differences between old and new IDF carbs with regards to the taper of the velocity stacks, and the bore diameters of the carb top covers that make the 70 series flow more than the 13/15 series. So even the two Webers can not be compared directly as the improvements of the 70 series must be taken into account.

They claim to install them "right out of the box". A couple of variables to consider: Did they synchronize the carbs? Did they adjust the air bleed screws? Did they adjust the mixture screws? Did they adjust the accelerator pump stroke? Did they check and adjust the float levels? How many progression holes in each brand of carb?

I'd like to see how Empi can keep the same bore diameter for a 40mm and 44mm carb.
Did anyone notice the fuel standoff with the 40mm Empi carbs at higher revs?

I'm not an advocate for Weber, but on the other hand, I don't advocate sending money and manufacturing to China. With an apples to apples comparison, you can't compare a granny smith to a golden delicious, they are different.

[So Cal Mark]

geez, this is so ridiculous. The Webers are new out of the box IDFs, the EMPIs are new out of the box HPMX. Yes, EMPI is touting the fact that they have improved over the original design that Weber came up with and has now abandoned. The dyno test shows what the improvements have accomplished.

[timinator]

They claim to install them "right out of the box". A couple of variables to consider: Did they synchronize the carbs? Did they adjust the air bleed screws? Did they adjust the mixture screws? Did they adjust the accelerator pump stroke? Did they check and adjust the float levels? How many progression holes in each brand of carb?

Hard to believe they could run almost identical horsepower and torque numbers with carbs that were not adjusted properly. Since the difference between the two carbs is approx. 1% it seems like they must have been spot on with the adjustment. Most back to back dyno runs are lucky to be that close on the same engine without changing anything. How many progression holes did you want?

[sptcoupe]

I agree with Mark, and as I said in my original post, the difference is absolutely nil. So if the idea was to demonstrate that EMPIs flow as well Webers, case closed. I really can't imagine what would make them flow significantly different anyway. None of the adjustments matter (idle mixture, air bleeds, throttle rod or balancing) at WOT anyway - they are on the main/air corrector circuits.

The engine condition will make much more difference in the way it flows than the carbs, by orders of magnitude. A set of Webers won't make a poorly prepped engine perform any better or worse than a set of EMPIs will make a well-done engine perform poorly.