those flow like 270cfm un-ported.

 

I have to think that the swirl plates and the runner shrinkage (and maybe the holes too?) were last minute efforts to get the thing to meet CAFE and CARB cert.

From a functional stand point, when you want efficiency, at cruising, where is the throttle? Damn near closed. So what's the air velocity and path looking like ~1" below the plate where the blades are? And at that point, what good are the blades even doing? In my mind, not much. At WOT, I could see the blades doing a "good thing"....but no one is concerned with CAFE or CARB at WOT. So....I think they're a band aid that made a tiny diff that helped them eek by govt. regs.

 

I agree.
It could be as simple as detuning the TBI to match the detuned runners, create more velocity, because gm already had the throttle bodies.

 

a couple of videos. one with diffuser, one without. Looks to me that the diffuser helps keep the mixture on the tb side of the manifold and with no diffuser it spreads out more.
going to take some videos from top instead of from the side. also going to check an unmodified diffuser. Looks to me that diffusers are beneficial.
want to flow all runners at once to see what that looks like.

 

From a different camera angle the diffusers don't look like they do much if anything. must help with fuel atomization, but I don't know. stock diffusers do restrict, but are ok with stock setup
I'm done testing.
stock head, manifold, TB's 145-160cfm. dart heads, ported manifold, modified diffusers 210-220. numbers are for comparison. 210 cfm intake with 190cfm exhaust = 393HP at crank in theory. I'm shooting for 350HP. fun project, hope it works out. can always put it back to stock. nothing ventured nothing gained.
time to put car back together

 

Awesome !

 

I can't see the vids, for some reason.

 

You are really making me want to test diffusers vs no diffusers on the dyno... dyno time isn't cheap but also isn't crazy expensive... but the lid is a pretty quick swap at least... I'm looking at it like this:
1. Stock unmolested intake manifold on my engine. (Done, results are posted in the other thread.)
2. Stock unmolested intake manifold with diffusers removed on my engine. (is it really necessary?)
3. Ported heavily molested intake manifold with diffusers. (I think this would be interesting.)
4. Ported heavily molested intake manifold without diffusers. (Curious what they're worth on something that will "tax" a pretty well ported intake.)
5. Same setup as 4 but with bored throttle bodies. (the stock units were a restriction on the renegade, are they on a ported manifold too?)
6. Renegade with ported throttle bodies. (Also have this in the other thread.)

And with the dyno it removes my inconsistency if I were to say... go to a track.

 

Dyno is better/faster/easier, but if the track were the option, the TRAP tells the story.

I bored Jim's TB's. On his stock engine'd dual exhaust/ported intake car the bored TB's did nothing. Obviously on a "bigger" engine, they'd make a diff.

 

Do you have *correction** "Data Master"?
With correct ALDL cable.
tunerpro has a built in DYNO. Capture a baseline.
Capture add-ons. Advantage. VS a chassis Dyno.
Realtime air flow. Realtime vehicle load.
Records all sensors.
NO hook-up time. No shop costs.
Mistake on a pull. Most count as a pull.
Mistake on TP. simply re- do.

 

thanks for telling me. I'll try again.

 

I was showing 10 KPa lower above 4400 with the stock units than the bored ones... they were definitely helpful. I felt and could hear (no intake whistling) the difference lol. But I agree... trap would be ideal, I'm just not sure I'm consistent enough to nail it every time... and I don't exactly think the 4+3 or dana 36 would appreciate me really hammering on it to get the best overall runs possible sever dozen times.
I suppose I could. Does tuner pro support that on say an ebl flash? I know the ebl has some built in tests but they're basic. I've got to play around with it a bit more... for now the car runs and drives. Once it warms up and I can actually drive it without dealing with the road salt. (I could but summer tires below 40 don't exactly work well to begin with) That and it's pretty buried in the garage at the moment...

 

they worked on my phone

 

Stock unmolested intake manifold with diffusers removed is plus 5cfm 155cfm. no diffusers clay radius entrance no other mod. plus 10 cfm. most I could get out of a stock unported runner is 160cfm
Ported heavily molested intake manifold without diffusers. my modified intake manifold, no diffusers, no head 227cfm. with stock diffusers 207cfm
also flowed 227cfm with modified diffusers

 

one thing I'm curious about is a mildly ported intake manifold with radius entrance.one problem with stock head is the port is smaller then intake manifold at top.


clay entrance stock manifold

 

*** Correction.
Sorry.. Make that.. Data Master OBD1 data logging.
Year specific. ALDL recording.

 

The problem with a big flat shelf like that sticking out is that it just doesn't block the flow equal to it's area.

If you look at one of my runner smoke videos you can see how the flat runner face deflects the flow out into the runner, in effect necking down the runner cross section.

Going to make the runners appear even smaller than they are, and the top of the runner is where the highest velocity and flow occurs.





Know it's a pain ... but could you stuff foam into the runners, tape off and drop cloth the engine ... and knock those edges down with a burr? with Shop-Vac going?

 

not sure I understand. I'm not using stock heads on car replacing they with bowl blended gasket matched dart 165ss heads .they ended up flowing 245cfm intake and 187cfm exhaust @.500. was trying to show one of the problems with stock heads and why stock head, stock intake manifold only flow 145 cfm. I must not have been clear.

 

I'm going to try to summarize what I've learned. good chance I'll leave something out.
completely stock 1984 corvette intake system flows 145cfm. the intake alone flows 150cfm and 155 without diffuser or modified diffuser. also stock heads need gasket matching, bad match causes minus 5 cfm with stock manifold. adding clay radius entrance to otherwise stock intake will flow 160cfm. this is the best that I did with zero porting. I believe a mildly ported intake and gasket matched head could yield 180cfm, maybe radius entrance, but not sure have not tried that. that's all that is needed for stock heads. headers, high flow cat and mufflers. maybe 280hp.
stock exhaust header pipe flows 115cfm, because GM pinch the pipe at the collector. pipe is 1.5" and should flow 165-170cfm, but it doesn't.
ported intake gained at least 20cfm with radius entrance. kind of tricky. For example, cylinder 8 runner cfm is affected by length of the radius that is added to 6. not the top of runner, but on the side.
tried .25" rod and .375" rod for radius. .25" didn't do much. .375 worked well. tried some .5" didn't seem much better and was worried about getting too close to top plate. settled for .375" rod.
my ported intake manifold 1.77CSA +/- flows 227cfm without heads, with top plate, TB's, no diffusers or modified diffusers. with stock top, stock diffusers 207cfm.
pretty much done. I'm tempted to do more cleanup for superficial reasons, but every time I have done that it changes the flow a little. It's like painting cars, there's a point where it's time to say it good.
cfm numbers are for comparison.
there is so many variables. I'm sure others can do better with different methods. I'm sharing what I did and the results, it could help someone else in the future. I have learned a ton on this forum.
dart heads are summit branded 165ss with 202/1.6 valves, 237cfm intake @.500, 138cfm exhaust @.500. intake has 5 angle valve job and exhaust has radius valve job.
with basic bowl blending, intake 245CFM @.500 and exhaust 187cfm @.500. didn't open up the throat. left them at about 84%. did the minimum port matching head slightly bigger.

 

Yes ... I knew you had better heads and thought maybe you where going to try the stock ones first.
I understand now