100 cfm more with anular and downleg boosters can't beat AFR

[Mattax]

I was downloading some AFR data (road testing the logger setup) with a jetting change and it led to looking at some older dyno data.
Long story short, the 750 cfm Holley currently on the engine was modified with annular boosters in the primaries and downlegs in the secondaries. However it never performed as well on the chassis dyno as it did with the plain ole '650'. Both are vacuum secondary 4150s.

After the 750 was modified, it ran very rich and its taken me a while (a long while) to get it pretty much in balance. I just leaned the main jetting a little more and was looking at the road results. It occured to me that the I might have a dyno run saved with 650 that had relatively rich AFR. If so, would it have similar power as the frankensteined 750 had when it was last on the dyno?

Sure 'nuff!

Just look at the AFR and power from 80 mph to 130 mph. Usually that's all that a dyno operator will capture and show you. (But I'm special and captured the shift. )

 

[Mattax]

Here's how much was gained by changing jets.
70,74 to 66, 72

 

[yellow rose]

Pretty cool. I need to start data logging. But I want to do it so I can log throttle position and MAP.

 

[Mattax]

Pretty cool. I need to start data logging. But I want to do it so I can log throttle position and MAP.

For logging I'm using the LM2 and auxbox. I still have my LM1 but wanted to try the LM2 since I bought it when I thought the LM1 died.
The auxbox included rpm, two g sensors and MAP. Adding TPS is on the to do list. I kept thinking I'll just grab one at a junk yard. It still hasn't happened. I've seen nice portable setup where the TPS has a lanyard to the throttle lever.

I have some dyno runs with the datalogger running. It's nice to have that in addition to the Dynojet's info. My plan has been to run it with the logger at the drag strip. So far that hasn't happened. This year for sure!
Today's drive on the roads got a variety of conditions but not the same as a dyno or drag strip.
I can put some screen shots up if you'ld like.

 

[yellow rose]

For logging I'm using the LM2 and auxbox. I still have my LM1 but wanted to try the LM2 since I bought it when I thought the LM1 died.
The auxbox included rpm, two g sensors and MAP. Adding TPS is on the to do list. I kept thinking I'll just grab one at a junk yard. It still hasn't happened. I've seen nice portable setup where the TPS has a lanyard to the throttle lever.

I have some dyno runs with the datalogger running. It's nice to have that in addition to the Dynojet's info. My plan has been to run it with the logger at the drag strip. So far that hasn't happened. This year for sure!
Today's drive on the roads got a variety of conditions but not the same as a dyno or drag strip.
I can put some screen shots up if you'ld like.

I'm thinking about an RPM data logger because I also need to log data for my clutch.

I just haven't pulled the trigger yet.

 

[DFX 340 Duster]

Well, by adding the annular boosters and the down leg, didn’t you make the Holley function like a Carter? Just add an adjustable air door to the secondary side and you have an AVS or ThermoQuad! (Wink, wink)

Nice work Mattax

 

[Dana]

For logging I'm using the LM2 and auxbox. I still have my LM1 but wanted to try the LM2 since I bought it when I thought the LM1 died.
The auxbox included rpm, two g sensors and MAP. Adding TPS is on the to do list. I kept thinking I'll just grab one at a junk yard. It still hasn't happened. I've seen nice portable setup where the TPS has a lanyard to the throttle lever.

I have some dyno runs with the datalogger running. It's nice to have that in addition to the Dynojet's info. My plan has been to run it with the logger at the drag strip. So far that hasn't happened. This year for sure!
Today's drive on the roads got a variety of conditions but not the same as a dyno or drag strip.
I can put some screen shots up if you'ld like.

Post away!

 

[Mattax]

Well, by adding the annular boosters and the down leg, didn’t you make the Holley function like a Carter? Just add an adjustable air door to the secondary side and you have an AVS or ThermoQuad! (Wink, wink)

Nice work Mattax

I'd actually love to try out the 'street demon' since its essentially a square bore version of the T-quad.
I just wanted to have this frankenstien tweaked a little better and use it as my backup/baseline.
My plan was to try a mostly unmolested 3310-2 next, but since the '650' already has jetting pretty close from the dyno work going to try that again. On that one I moved the kill bleeds back to the angle passage where they belong. So very curious how that effects the start of the mains.

The annular boosters were my idea - because Vizard really pushed it in How to Build Horsepower. The downlegs QF installed on their own impulse. Much later Bruce "Shrinker" Robertson rightly pointed out that's putting different droplet types into different cylinders. which is kindof nuts, especially for a hobbiest.

 

[Mattax]

OK. Here's some I've already made screen shots of and marked up.
750 on the chassis dyno.
Solid lines is run #31, which is very similar to the 33 shown in the first post.
Dashed lines are an overlay of an earlier run with larger secondary jets, and a different pair of secondary emulsion holes.

Changes in power are difficult to ascertain as the rpm slope is the only clue.
But it is easier to see the details of the AFR and vacuum.
Those downlegs are going lean, then rich before drifting lean with rpm.
That's why in the photo of the carb you now see wires in the secondary main air bleeds. Would like to get back to the dyno or drag strip with the logger to see how much correction they are doing. I've also moved the secondary IFRs to a low location but that shouldn't anything but the start - if that.

Next is some relatively low speed vacuum crowds. In other words, using the throttle to hold a vacuum reading.
This is the 650 carb and the mallory built MP distributor. With the converter tightened up a little, there were part throttle ping issues and a dead spot that was totally unacceptable for autocrossing.

The vacuum readings seem to be about 1.5"Hg higher than the mechanical gage. May be something to do with my conversion or the MAP sensor.

We can see that increasing throttle brings with it leaner mixture (violet), and more acceleration (orange), until vacuum drops below 12" on the MAP reading. Then AFR gets ragged and there's no corresponding increase in acceleration.
If this was done at higher speed, we'ld know that the power valve needs to open at this point. At these speeds, it was a maybe. Notice it did a little better at 2800 rpm. I think the kill bleed location was causing a delayed reaction on the main circuits. To be continued...

Throttle position would be helpful. It would let us better estimate how much portion is from the transfer slot vs booster, and also see motion related to pump shot.

 

[Mattax]

Here's how much was gained by changing jets.
70,74 to 66, 72
View attachment 1715473374

Just wanted to point out that the WBO2 was not neccessary to see the improvements made by changing jets.
In this case I'm glad it was captured because it reveals the jetting is starting to get out of the best relationship with the main airbleeds. But if we aimed for 12.5:1 we would have left a serious amount of power untapped. This engine made more power around 13 to 13.2

On the previous engine with the relatively unmodified 3310-3, we got best jetting based on mph at the drag strip. Some tracks had both 1/8 and 1/4 mile data on the time slip. That's always nice, esp when you're not a real consistant getting the car off the line. LOL.

 

[Mattax]

Here's a table from early in the calibration saga of the modified carb.
Every big change got a new letter. So E is the 5th big change (as I perceived it) and 3 is the third version within that.

Tables are best for steady conditions. Slamming the throttle open usually causes brief rich or lean spots and these can't be seperated just by looking at the chart. It is possible to select around them when creating a chart. I did not do that in these examples.

The green descriptions were my early attempt to undertand the relationship of the throttle to the MAP and RPM. I've refined it as you'll see.

Next table is made from the recent road test.

Changing the the data shown from AFR to Acceleration results in this:

Blue highlights deceleration. The data along the line of zero acceleration is going to be mostly steady cruising data.
Transfering the black line marking steady cruising onto the table showing AFR looks like this.

Throttle position is roughly the diagonals shown with green arrows pointing toward increased opening.
As the speed increases, more throttle is needed to maintain steady speed.
When cruising above 2800 rpm, the main circuit is providing most of the fuel.
At lower speeds and less load the idle circuit (transition slots) provides most of the fuel, and the main circuits contribute only as the throttles are opened for acceleration or hills.

This combination probably could be jetted a little leaner and like it. But it looks like it might want the enrichment at higher vacuum. So next change will be a 8.5 PV instead of the 6.5; or maybe 10.5 - depends on what is in the box.

 

[AndyF]

At this point you should just spend $1000 and put a Holley Sniper on there. You would gain a ton of information and be able to dial in the tune much easier.

 

[Mattax]

No.
At this point I've learned alot. Nor do I need to give your pals a grand, plus the time and money to rework the fuel and electric systems.
But the basic lesson here is that a wideband or any these blingy contraptions are not essential to find power and economy with a good basic carby.
All that's needed is a few jets and a way to measure performance, whether its a dyno or a track.
That would have required reading the first two posts.
The other ones showing some logger samples were by request.

 

[Mattax]

A little follow up here.
In posts #1 and 9 the dyno runs reveal the downleg 750's secondaries were drifting lean from mid to top rpm.
So a question was whether I was able to correct that?
Focusing on just high rpms from the dyno that day and the one 1/4 mile run from last year we can see the answer is yes.

Dyno run #32 (same carb config as in first post)

Drag strip run focusing 2nd and 3rd gear.

Secondary high speed airbleeds reduced from .033 to equivalent of .029" dia.
In 2nd gear from 5000 to 6000 rpm, and in 3rd from 4700 to to the 1/4 mile stripe the AFR is now pretty flat.
Because the AFR was staying flat at the top the secondary jets could be further restricted without fear of going too lean.
In addition to jetting the secondary jets 2 sizes smaller, the secondary idle restrictions were moved to the low location and the secondary IABs reduced.

What is going on below 4700 rpm is harder to figure out.
The challenge with only one 1/4 mile run is twofold.
A. Although I got the car off the line pretty well I was rusty and unprepared for how quick the car was pulling. Result was I lifted a little and didn't keep the car truly straight down the track. Additional runs would have been good.
B.While the dyno run had the vacuum secondary opening controlled with a yellow spring, in the quarter mile run a plain spring with slower opening was used. Why? Because my intention that night was to change springs between runs. That never happened.

Looking at the vacuum (blue line) it seems reasonable to conclude that the secondaries late and slow opening may have contributed to richer conditions after the shift. We can see that at the 2-3 shift as well as the 1-2 shift. There may be more to it - maybe the secondary idle circuit is a bit rich.

 

[Bewy]

Mother Mopar was right.....Put a TQ on it.

 

[Hysteric]

Mattax is that afr trace smoothed or raw?

Also what's happening at the 3.30 - 3.50 mark with the afr?

 

[Mattax]

Mother Mopar was right.....Put a TQ on it.

There's nothing wrong with a TQ but your post irrelevant to the topic. It's not about my engine or whether one type of carb is 'better' than another.
There's plenty of threads discussing, arguing, and some name calling about that, but that's not the topic here.

 

[Mattax]

Mattax is that afr trace smoothed or raw?

Also what's happening at the 3.30 - 3.50 mark with the afr?

It should be raw.
As far as what is happening at 3.3-3.5 seconds, that's what I'm talking about when I wrote I'm not sure what's happening up to 4700 rpm in 2nd gear. Looking at the rise in manifold vacuum from 31.5 to 33 sec, it seems most likely the secondaries aren't opening soon enough. The velocity past those big boosters is certainly very high. Also the primary PVCRs probably need to be smaller.

Look at this run with no secondaries.

We see a similar rise in vacuum once it goes to wide open throttle.
Also the AFR was 12.2 with 65 PMJ and on the track the AFR is around 12.3 up to 4700 using a 64 PMJ.

 

[yellow rose]

It should be raw.
As far as what is happening at 3.3-3.5 seconds, that's what I'm talking about when I wrote I'm not sure what's happening up to 4700 rpm in 2nd gear. Looking at the rise in manifold vacuum from 31.5 to 33 sec, it seems most likely the secondaries aren't opening soon enough. The velocity past those big boosters is certainly very high. Also the primary PVCRs probably need to be smaller.

Look at this run with no secondaries.
View attachment 1715678588
We see a similar rise in vacuum once it goes to wide open throttle.
Also the AFR was 12.2 with 65 PMJ and on the track the AFR is around 12.3 up to 4700 using a 64 PMJ.

Interesting that you can use a 64 MJ on that 3310. I’ve been rather anti annular booster in 4150’s since I had such a bad experience with them a long time ago.

This is one of those things that I need to revisit. At this point, I think maybe any cold air intake, and especially something like a tunnel ram needs annular boosters.

I could be wrong on that though. I’m wrong. A lot.

 

[Mattax]

It would be interesting to do more experimentation with this. Smaller boosters would be probably be a good thing.
I'm thinking like yoiu about anulars - in certain combos they can help distribution but where the temps are too high in the intake tract probably contribute to early vaporization.
We'll see what happens but my current plan is to try out the 650 on the track, followed by comparing with a 3310-2.
Would really like to then compare with 4776 or 4777 but one will have to fall in my lap.
Time, money, place to store more carbs = reality. So realisticly I expcect the 650 will get tested this year.

 

[yellow rose]

It would be interesting to do more experimentation with this. Smaller boosters would be probably be a good thing.
I'm thinking like yoiu about anulars - in certain combos they can help distribution but where the temps are too high in the intake tract probably contribute to early vaporization.
We'll see what happens but my current plan is to try out the 650 on the track, followed by comparing with a 3310-2.
Would really like to then compare with 4776 or 4777 but one will have to fall in my lap.
Time, money, place to store more carbs = reality. So realisticly I expcect the 650 will get tested this year.

That’s where I’m heading. Since I predominantly use cold intakes and I like no more than 180 degree engine temperatures (I’m going to see if I can get that down to 160 this year) it would seem like an annular booster would be the best option.

Plus, I generally run bigger carbs than most so that would add up to annular too.

 

[TT5.9mag]

@Mattax any idea what kind of flow restriction the annular boosters Caused in your particular case? Seems with a choke horn they take up a whole lotta space there. Do you have any data from the 750 before and after the booster change?

 

[Mattax]

No I don't. I agree they take up a lot of space in venturi.
I never thought they were going to put such big boosters in! My understanding was they were going to be something like a truck avenger booster - and in all 4.
So one reason I bought a relatively unmolested 3310-2 is to compare.
Unfortunately while now I have more time, getting time at a track or on a dyno is now more difficult. Such is life.

 

[yellow rose]

@Mattax any idea what kind of flow restriction the annular boosters Caused in your particular case? Seems with a choke horn they take up a whole lotta space there. Do you have any data from the 750 before and after the booster change?

It depends on the booster. I’m very green on these boosters, but what I’m finding out is the better boosters are a SLIGHT CFM air reduction.

Which, comes back around to the old saying “not all airflow is good airflow”.

If a slight reduction in air flow cleans up distribution, allows less total timing (within reason...in my opinion no way will a chamber that runs at say...35 degrees will ever run at 28 degrees if everything is perfect...you may get down to 32...maybe), reduces required MJ sizing and such, then I consider that an easy thing to give up and a win.

Because of the way most engine dyno’s measure power, a booster change may not show up in anything but the BSFC number. On an inertia dyno, that lower BSFC number will translate into higher HP numbers.

On the other side of the coin, you can atomize the fuel too much and lose power right quick. A heated intake manifold, engine temps for catalytic converters and such will atomize the fuel too much and drop power.

I have at least 6 carbs that are getting annular boosters this year. It may suck hard on all of them. I hope not, because that’s going to cost me an arm and a leg.

 

[TT5.9mag]

No I don't. I agree they take up a lot of space in venturi.
I never thought they were going to put such big boosters in! My understanding was they were going to be something like a truck avenger booster - and in all 4.
So one reason I bought a relatively unmolested 3310-2 is to compare.
Unfortunately while now I have more time, getting time at a track or on a dyno is now more difficult. Such is life.

Got it. Thanks. I’ve heard they do reduce flow quite a bit. But I have no data to support that. If you’re interested I have a 3310-6 center here with no choke horn and radiused entries I could send you for testing. It just came off my big block for a CSU blow through. I’ll send it to you if you’d like. Just send it back when you’re done and post the data.