Did you see any better mph with the 58mm tb wth and without filter

 

Those measurements were on the street...have not been back to the track to measure ET/MPH improvements yet.

 

Chris:

My '1"Hg' comment is just a very rough guideline, based on what I have seen. It is not "gospel".... just a comment for trying to help people locate problems. I need to pull up a couple of data logs from some of my NA passes to see what kind of pressures I am seeing with my modified WS6 configuration.

Are you running the full WS6 intake? Are all the baffles still in the hood? Are you using the Fernco or the stock connector between the MAF and TB? Do you have the full grid on the airbox cover?

When looking at the numbers, you really need to calculate the pressure loss from atmospheric.... BAR - MAP. That will tell you the exact loss.

As far as the 20+mS pulse width, what program are you reading those with?

Fred

 

Fred,

I am reading/scanning with Car Code from Alex Peper (the poor man's Autotap). Frame rate isn't what I'd like it to be but its proven itself fairly reliable/repeatable.

Anyway. I do have the Fernco piece, but the baffles are still in the hood and the grates are still on the lid. Those grates are probably coming off today

Here's some more logging results with a paper filter and then the lid w/no filter:

W/lid and paper filter
Low MAP ---92
MAF ---273g/s
injectorPW---19.94
(This is all still better than before except the MAP. 92 appeared to be a spike, 94 was more common)

W/lid only, no filter
Low MAP ---94
MAF ---287
InjPW ---19.94

Appears most of the restriction is in the filter, although I am still going to cut the grates out of the lid.

These are SVO 24# injectors and I knew with this much Cyl head and cam that I was going to be at their limits. That's why the 30#'s are arriving today

 

have you tried a different MAP sensor?

 

I think that how much seat pressure is needed has a lot to do with exactly what lobes you are running. I know of mild solid roller setups with ~150lbs on the seat that seem to work fine. In fact, Comp recommends the #977 spring for a lot of their street rollers. That spring is supposed to be 155lbs on the seat. Now, I am not one of those people who advises listening to everything a manufacturer says, they don't know everything and have a variety of motivations for saying what they do. And Comp in particular gives some screwy advice on their tech line. But I have found their catalog to be pretty accurate. So while I am not going to argue with the folks here who actually run solids rollers in their own LT1's, as I do not, I just want to raise a small bit of dissent.

Rich Krause

 

I've been thinking about this very thing the last couple of days...I search and here's a thread!

Thanks for all the data points, Chris. Very interesting. However, as Fred said you really need to compare the MAP readings to the current barometer as I do below.

One question--did you notice any difference depending upon the gear/speed? Keith showed long ago that the WS6 hood is actually a restriction at low speeds.

Well, here are my results. The car is a cam-only LT1 with stock heads, stock intake, stock TB, stock MAF, G2 CAI and a Cut Stock Airbox with a K&N. Probably not the best intake setup--long story.... Anyway, here are the results:

Two days ago, with everything in place:

http://www.jonaadland.com/NewPics3/LogAirbox.JPG

As you can see, I have quite a pressure drop across the intake tract. Even though it might not necessarily be where I make peak power, I chose to zero in on 6000 RPM since it was a nice round number that others could duplicate even with a stock engine. It also gave me room on both sides of it to take an average--given the sample rate and the slightly choppy curves, I don't think the "snapshot" of one record should be looked at as representative of the overall picture.

I took the 6000 RPM record, the two before and the two after and averaged them. That gave me an average MAP of 92.56 kPa. With the baro being 99.7, that’s a pressure drop of 7.14 kPa, or 1.036 psi for a ratio of 92.56/99.7 = .928. So maybe my cut airbox isn’t so hot….

Today I remove the airbox, leaving the end of the G2 elbow hanging and made another run:

http://www.jonaadland.com/NewPics3/LogNoAirbox.JPG

Now that’s a little better. This illustrates the importance of referencing the MAP to the baro—it’s different than it was two days ago. Using the same method as above gives an average MAP of 95.44 with a barometer reading of 101.1. That’s a loss of only 5.66 kPa, .821 psi, a ratio of .944—much better. If I’m somewhere close to the 350 RWHP range, one could estimate that the airbox/filter is costing me (9.44/9.28-1) * 350 = 6 RWHP. That may not sound like much, but hey, every little bit counts.

Now the question becomes how much will I lose back by replacing the airbox with a large conical filter (yes, I need a filter!)? Five of the six? One? Heck, maybe the naked round end of the G2 elbow flopping about caused so much turbulence I’ll actually gain power by installing a big conical filter. There’s only one way to find out…. Even if I only gain 3 HP, from a $30 filter that’s not bad. 1$ per HP is money well spent.

I know most reading are interested in TB’s, MAFs, etc. Well, I overspent this year’s budget long ago so I won’t be testing any of those things anytime soon. The biggest reason for my posting this wasn’t to provide test results but to show my methods so others can easily duplicate them. I know many here have logging software. There’s no reason you can’t do exactly what I did above. You might not even have to get up from your computer—you may already have the runs you need to look at on your hard drive. About the only additional suggestion I’d have is to make several runs with each set-up and average them to increase accuracy.

Testing something for yourself and getting analytical results you can have faith in beats taking somebody’s word for it any day in my book.
Please do!

So, anybody else have some logs you want to post? How much pressure drop is there across your intake?

 

Wow, really dug out of the archives. But I'm glad you did because I must have been away at the time and missed the whole discussion.

FWIW, I lose a bit less than 6kpa from Baro pressure, and between 4200 and 5700 (sampling that I just happen to have graphed) my best is about 1.5kpa from Baro.

So if I just subtract the two, it looks like as the RPMs rise, I lose at most 4.5kpa of additional pumping loss. But, a higher differential pressure (between manifold and atmosphere) would equal a larger vacuum, which would pull more air through the orifice right (so with that logic, the loss isn't even as great as it would appear)? All in all, I can't imagine that 4.5kpa differential making all that much of a loss. Now if there is a 4.5kpa loss in barometer pressure, well, that is a different thing all-together (I have to live with a loss of nearly 12kpa baro all the time thanks to 3750' of elevation and it really bites on NA power).

Maybe one of the board engineers can correct any bad thinking above.

Also, FWIW, my VE numbers are better at the higher RPMs even though my pumping losses appear to increase in the same area.

 

No... that's not the way it works. Lets keep it simple, and assume that we are not dealing with pulse tuning, overlap and all those complicating factors. Let's assume barometric pressure is 100kPa.

As the piston drops, the only thing that "PUSHES" air into the resulting void is barometeric pressure. If we ignore the pressure losses in the head runner, there will only be a vaccum in the intake manifold if something is preventing the full barometric pressure from being there.

It doesn't mean the large vacuum would pull more air in.... it means there is something between outside barometric air and the intake manifold that is robbing pressure and creating the vacuum. Think of it this way... the only reason you have 20"Hg vacuum at idle is because you have intentionally placed a 20"Hg pressure robbing device in the inlet air track.... the closed throttle body blade(s). With your theory, when the engine is at idle and the manifold is at 33kPa (20"Hg vacuum), the air would be flowing like crazy because the vacuum is so high. Not the way it works.

The vacuum at WOT (4.5kPA) exists ONLY because there is pressure loss in the air intake system. If you only have 95.5kPa in the intake manifold, you can't have more than 95.5kPa in the cylinder (remember, we're keeping this simplified). If you only have 95.5kPa in the cylinder, you can only make 95.5% of the power the engine could have made without the pressure loss. A 4.5kPa loss (referenced to 100kPa barometer) LOSES 4.5% power. Doesn't matter whether the pressure is 95.5kPa because you are at 1,200-ft altitude, or because obstruction in the intake track lost the 4.5kPa.

4.5kPa costs 4.5% of the HP. At your altitude, it costs you an even larger percentage of the power.

 

Ouch ouch ouch lol, now I'm going to have to think this all through again.

<--- goes in the corner licking his wounds lol.

I guess the way I was relating this is that the piston moving down creates vacuum right? And a larger differential pressure between the inside of the intake manifold and the atmosphere would "pull" the air in right? And the larger that differential pressure, the more air will be pulled through a given orifice size right? But maybe what I'm missing is the pressure loss caused by that vacuum decreasing the absolute pressure (and thus mass) of that volume of air (wow, does that even make sense or can you infer what I mean lol)?

I was relating off of a flow bench's pressure differential. I.E. 28"h2o flows more air than 20.4"h2o for a given orifice size.

So along those lines then yes, at idle 33kpa of vacuum is pulling in crazy amounts of air compared to say 1kpa of vacuum through the almost closed or just IAC orifice.

I *think* what I am missing is the "baro pressure filling the void" part. And how MAP effectively becomes the "baro pressure" seen by the inside of the intake manifold.

Keep edumacating me