Denny,
I don't know which throttle body you're running but I remember reading an article where John Lingenfelter was talking about the Accel 58mm tb and how it flowed "1000 cfm".
Which just brings me to my next point which is... if they're flow tested at a 1.5" Hg pressure drop like carbs then you are going to see a restriction (if EA is being truthful with it's air demands calc... more later).

If it truely is a 1.5" Hg rating then your flow at 1.0" Hg is 816 cfm and at the high range of acceptable, 1.1" Hg, she'll do 856 cfm.

CFM/sq rt (Old pressure drop/New pressure drop)

Now, if we take EA's calc (~920 cfm) and apply that to find air speed through the throttle bore I'm calculating 330 feet/sec! I made a quick spreadsheet that calculates this, using throttle shaft diameter as a variable in calculating "effective bore area".

That's way too much speed through the throttle, which should be ~220-240 feet/sec.

If I take your 398 ci engine turning 7000rpm at 90% VE, I get 726 cfm. I don't know why EA is getting something so much higher? Out of curiousity, what is it showing you for VE?
Anyhow, by my calcs that's 257 feet/sec through a throttle diameter of 2.283" with an effective area calculated at 3.382 in^2.

So I guess what I'm getting at is... even a 58mm tb is too small for an engine of this size turning this much rpm. The engine would show some gains with an even larger throttle body and interestingly enough.... if you look at the air speed of a stock throttle body, on a factory stock engine turning to stock peak power... it shows that GM sized the thing to flow ~260 cfm at that rpm.
So my theory is that anything slightly hotter than stock is going to need and will show gains (proportional to power increase) with a larger throttle body.

Beg, borrow or steal a monoblade and try it out. I think it'd be worth your time.

edit: If anyone would like this spreadsheet, just PM me. Nothing fancy, just threw it together real quick... but useful. My opinion of course.

-Mindgame

 

Mindgame

Monoblade…..I may have to buy one, but the issue isn’t so much in the throttle body as it is in the intake. Once you port one for a monoblade, there is no turning back and it’s got a lot of porting done to it to throw away.

We installed the 36lb injectors this morning and they didn't help. In fact, the car now is rich on the top end and isn’t responding very well to tuning on top. Being it’s now rich, our gut feeling is we have run out throttle body but the responding to tuning issue usually means with 200 miles on the engine, it’s still seating some.

Performance Trends Volumetric Efficiency…… from 5450 rpm to 6575 the program is showing about 110% and at 6800/108 and @ 7025/105.7% efficiency. To be candid, I only trust the software so far as its close most of the time, but usually no cigar.

Camshaft…….Something new has popped up. The car is making right at 460 rwhp and it’s a bit of a difficult decision as it breaks 450 rwhp around 5600 rpm, currently peaks @ 6100 rpm and @ 7100 rpm it still makes over 430 rwhp.

Even though it’s only 245/248 duration, but with 222cc intake ports I expected it to peak a little higher. Maybe because it’s not 100% yet as to why it’s peaking earlier. With the powerband it's got, really tuff call on more duration as it may make more peak power; but be slower overall.

Going to go ahead and order the monoblade for right now and put some miles on the motor to see what it does before I worry about the cam. May even do some 1.7 rockers first.

As usual…. Thank You very much.

 

Denny,

Going to a monoblade opening doesn't junk the intake... You can still run a 58mm TB on it even with the monoblade opening... it's not a problem at all.

I think part of the issue with the software is the pleanum volume and the fact that the program doesn't respond to changes in that as much, try putting a pleanum volume in that's MUCH less than you think it is. More you have the less TB you need. Steve Quinn's Modified LT intake added runner flow and pleanum volume, both are needed with higher airflow demands that good heads, cubes and RPM put on these things.

Bret

 

It's been a while since I last owned a monoblade, but what about the IAC opening in the front of the intake? If memory serves me correct you cut into the opening and then have to either weld or JB weld it up.

Wouldn't that prevent going back to a 58 mmtb???

 

The a/f actually richens up above 6000 rpms and with the vacuum readings at high rpm I think its a airflow problem since the injectors are still adding fuel but if we are lacking airflow that would cause the a/f to richen up
...Scott

 

The MAF sensor can be maxing out at 450 rwhp. It would cause the car to run rich at high rpms and not pick up any power.

 

We (as in A&S Automotive - Scott) ran the car in speed density mode to see if there was a MAF issue and it didn't show up doing so. If there is a MAF issue, can it just be corrected by MAF calibration? We are running billet ends with stock MAF center.

 

You don't have to really do anything to the IAC hole.... It just goes into the IAC passages under the runners. It's actually better to have the IAC passage open to the rest of the pleanum IMHO.

Bret

 

Well good...... you saved me about four bucks on JB weld. Now I can do another motor with the money I saved.

 

Denny - I'll be in Dallas on Monday-Tuesday next week. You are welcome to try my Monobalde if you want...I need it back for the weekend though.

http://forums.corvetteforum.com/phot...ake_2_-med.JPG

http://forums.corvetteforum.com/phot...intake-med.jpg

 

LOL

 

Very, very nice and I appreciate the offer. Afraid one will be sitting on my doorstep tomorrow morning and I’ll be wacking away on the intake soon after.

Very generous and thanks for thinking about me. I just hopes it works.

 

A ported MAF can support close to 500 rwhp with a proper calibration. I would keep an eye on blms to see if the calibration is good.

 

Just looked at those monblade pics LT4POWR... nice intake ;-) Kept thinking I like how those areas were all machined clean of powder where you mount ****.... then I was like HOLD ON. lol

Bret

 

Just as a FYI we already have the monoblade on the car but got thrown a monkey wrentch into the deal. The new Venom 36lb injectors seem to have issues so we had to thrown the 30’s back in for now. One lost a plastic tip and another had a leaky body. Nice………. Good old aftermarket.

Ordered out new ones and we’ll see how it does with 36’s and a monoblade but we basically lost all our tune so I just set the computer to 30lb injectors and added 10% fuel to get it ballpark.

We’ll get it on the dyno next week and see if the monoblade helps.