I posted this in another thread in the parts wanted section but thought if might deserve its on thread. Some of my thoughts on the First intake system.


Let me say that if you can get 1.9" ID tubes (and you can) on the FIRST alot of good things will happen. Plus you can port the base to match the CSA withour welding. IMHO this will allow the motor to rev up high enough to pick up the 2nd harmonic wave. Most of the time we are dealing with the 4th and 3rd harmonic wave.

The 2nd harmonic wave is the strongest and has the widest rpm range. Check this link out. http://www.bgsoflex.com/intakeln.html and type in the total runner length such as 21 inches. This includes the head from the back of the valve all they way to the plenum.

The bottom line is we are trying to fill the cylinder with as much fuel/air as possible. Three things help us out with that.

1. One is exhaust overlap where the exhaust gases are helping to pull in the air on the intake side during the overlap period.
2. The ram air effect by the column of gases in the intake runner track. This is a big player.
3. Wave tuning. With a 21 inch intake track you will pick up the 4th harmonic, the 3rd harmonic and the 2nd harmonic providing the CSA is large enough not to choke the motor.

I suspect at 1.9" diameter would do the trick. That is 2.83 in. sq. With a decent camshaft and good flowing heads such as the AFRs, I would think some real horsepower can be made and from a long runner intake system at that.

 

interesting,i was very close to get a FIRST intake but i went with the Super Ram
since its between LTR and STR
Thanks for the info about the harmonics !

 

This is interesting. I've knew about the effects of harmonic frequency...but hadn't considered the 2nd and 4th waves as a "viable option".

Where I read about it, years ago in this article:
http://www.hotrod.com/projectbuild/1...ing/index.html

...they claim that the third harmonic is the best to target. However, I can see why the second would be stronger and more effective.

 

Yes an interesting article. Most what you see written pertains to carburetor systems. EFI is another story because we do not have to worry about the fuel remaining in suspension or making turns. That is the reason the Chrysler guys went after the third harmonic because it does not require as long an intake tract and the fuel will remain in suspension better.

The manufacturors also go after the 3rd harmonic because of "packaging" or trying to fit everthing under the hood. However with TPI the "packaging" is already there. The problem with TPI from the factory as everyone knows is the small CSA of the runners and/or intake tract.

That is where the First comes in. You can open it up to a good size CSA and solve the CFM problem. It can easily be opened to a Felpro 1206 gasket(slightly less for no lip) and maintain the CSA through the base. Open the runners to a 1.9 inch diameter or so and presto you are there. You will have a long tube runner system making peak power around 6500rpm and along the way picking up the 4th, 3rd and 2nd harmonics. Peak torque would be around 5000rpm.

The CSA can be adjusted for your engine size and the runner length can be adjusted by siamesing the inlet runners at the plenum.

 

This is something I contemplated myself. For a couple of reasons, I questioned whether is would be worth grabbing for the 2nd order harmonic. But, if anything could signficantly leverage it, the FIRST would be at the top of the list.

As you, I used 21" and the same calculator to determine where that 2nd order harmonic hits. You'll notice longer runners bring it down lower. As runners get larger and larger (in diameter), you have to think their internal pressure rise drops. There was another calculator running around that factored in diamether IIRC.

Recently, I posted a graph of the FIRST intake using EA Pro. The calculator linked must be very close to the calculations used inside EA Pro because the harmonics are clearly visible in the graphs -- and they correspond quite nicely to your calculator (post#1). (I'll repost that simulation here if you like.)

What I see in the simulation is a drop of 100HP from 4800 to 5600 rpms. That's the gap between the 2nd and 3rd order harmonic. Furthermore, that drop in power exceeds 10% of peak power production. So, even if the 2nd order harmonic added 10% power back in AND WASN'T ACCOUNTED FOR BY EA Pro, my simulation would only regain 35 of the lost 100hp.

Even with a 10% bump at 5600rpms, I'm not convinced you could get up to HSR/MR levels at those rpms. Obviously, the 2nd order harmonic can't hurt AND the extra diameter would increase it's affect, but the 3rd and 4th harmonics might drop as pressure lowers from increasing diameter.

The prospect is intriguing though. Certainly, you've been a pioneer of experimentation with the TPI setups. More importantly, I have noticed that the FIRST seems to trade off the least in lower rpms to gain extra performance in higher rpms -- as a direct result of it's larger tubes. So, there's no doubt in my mind that it's the best TPI intake out there.

 

Interesting comments and food for thought. I just wonder if EA Pro accurately models that portion of the harmonics. 100hp is a lot to loose and from an averaging stand point I don't think you would get it back as you stated.

One of the reasons I wonder is there are two other factors working in our favor. One is the overlap period where the exhaust is helping to pull in the F/A through the intake valve. The other is the ramming/inertia effect of the air being stopped at the back of the intake valve and still building pressure in the take track until the valve opens again. The wave tunning as I understand it just builds on top of that at certain rpm levels as noted in the calculator.

As the wave harmonics ebb and flow that is what you see on the dyno as dips or valleys between each harmonic. Interesting as I was reviewing some old dyno charts on the TPI shootout many years ago and on the torque curve you could see the dip going from the 4th to the 3rd harmonic. It was not as noticeable on the hp curve versus the torque curve.

I am going to build up a long runner TPI system and see what happens. I will weld up an Accel TPI base to get the CSA I want. Make up a set of 2" runners with 1.875" ID, modifiy a factory plenum to fit and also increase the volume of the plenum. I will be shooting for around 21" total runner. I will be using my AFR 195 Comp heads. Should be able to have it all done by sometime in February. Maybe dyno in March.

If the dip is indeed to much between the 3rd and 2nd harmonic then I will revert back to the third harmonic and optimize for that. The possible rewards are good if it works.

Just had a thought. On EA Pro try it with no taper to the runners. Just a 2.76" CSA all the way through and see what happens. The AFR 195cc heads have a runner of 5.333". So the base and runners would be 15.667".

 

My impression -- from the very experienced builder running my simulations -- is that EA Pro is very accurate. And, as mentioned, the dips/humps in their simulations DO match the runner-length calculator you linked.

Yep, 15-17" is what I was shooting for (with my mega-SLP intake) --AND-- what Lingenfelter went for with his superram. Too bad they don't make a SR on roids -- just like the FIRST!

Between the FIRST and the SR though, I'd probably bet on the FIRST in a race. As you pointed out, tube-size is a big part of the equation.

 

1989, are you the same guy from 3rd gen that did all that welding and porting to a bigmouth base and SLP runners?

I'd love to see the results of someone trying this. It almost seems like you'd want unique cam timing to take the most advantage of the harmonics. Don't know though. My questions are; how well would this theory really play out, and what about the approach angle as compared to the HRS/MR etc.

 

Hi Tom

Yes, actually it was a First base and highly modified SLP runners. It did quite well with the 355 motor with peak power at 6500rpm. I had it optimized for that motor.

I have since built up a 369" SBC which got 539hp on an engine dyno at 6500rpm with a Victor Jr and carb. I figured the ports I did on the First base might be a little small for the new motor but they were ceramic coated with a temperature barrier and I did not want to mess with them thinking I could slip by.

Well, I took the new combination to the chasis dyno and the motor just choked at 5500rpm and 396RWHP. Yank PT-4000 stall and a 4L60E. So maybe around the 500hp mark at the motor. So what to do, what to do? By the way throttle response is incredible with this motor. It really lights the tires in 2nd gear. So much so I am having my GTA rear wheels modified to 17x11.

Well in the meantime Dyno Don has a First intake system at his shop and we took the base and a runner set over to Joe Shermans to have it flowed. My original flowed 301CFM out of the box using port one and that is one of the worst. This time using port 4 one of the better ones we got 314cfm. Then we attached a runner and that dropped it to 292CFM all untouched. Hmmmmm, the brain cells start stirring once again. I thought there would be more of a drop.

With some research including harmonics, flow, CSA, runner volume etc. I decided to try a long runner system again but on steroids. A friend had an Accel base available and after looking it over it will do the trick with modifications of course. Hey nothing that a little welding and machining won't cure. So that is where I am at.

Yes, EA Pro is very good. That is why I will have back up plan if things don't work out. Hey, what can possibly go wrong?

 

What are your thoughts on the superram? I am in the process of getting one and must admit I don't know too much about it.

 

I like the SuperRam. I would tune it for the 3rd harmonic range. I am in the process of working on the runners and plenum for one now. The base was already done by Dr J. I plan on shortening the runners a couple of inches so peak horsepower and the 3rd harmonic will peak around 6000rpm with a shift point no later than 6500rpm.

In fact the SuperRam may well be my fall back position if the long runner does not work out. I will make my own two inch runners and modify the plenum as needed.

 

Awesome stuff. I LOVE the work that youv'e done and the data that you share. Pleas keep us posted with all of your progress. Very interested, here.

-Tom

 

Will do.

 

Keep me posted on yours shootme a link, pm or something want to see how yours comes out. You probably know I just finished a SR and am having it flowed on a 195 AFR real soon. Nice to compare notes, sure if youre going nuts and welding on one it should really move some air.

 

 

Just doing a little welding and opening up the SuperRam runners for someone. I have broken through before in the bottom bolt hole area going to 1.75". Customer wants to go a large as we can. So I will have to evaluate it to see how far we can go. The runners are currently at the welding shop.

Also the one side bolt is real close where it is relieved. So I put a "stud" in those two areas, weld it all up and use longer bolts. It also helps during the install because the bottom bolt can be a pain to get to. With the longer bolt it makes it much easier. We will not be flow testing this one so no comparisons.

I was looking over the SuperRam plenum today in case I have to go that route and it looks like it would be real easy to use 2" tubing from the base to the plenum. The opening in the plenum is close to the size of a 2" tube now. By the way for aluminum tube 90 degree 2" x .065" wall it can be had with a 2" radius. I am using 3" radius U-bends for my long tube runner project. Also 2.5" radius U-bends are available. So plenty of options for those wanting to experiment.