Dyno Don

In our never ending quest for a better flowing TPI intake, we have the lastest results to report.

If you have been following this thread:

http://www.thirdgen.org/techboard/tp...?highlight=tpi (Visual TPI intake manifold ports)

You know what we have done so far.

The new manifold and engine combination was tested on the DynoJet dyno this Saturday. The results, again have us scratching our heads.

Not that they are bad, but we still have yet to achieve our goal of making more HP above 6000 RPM's.

Here are the Dyno graphs:
Judge for yourselfs, and feel free add your $.02.

It would appear the throttle was lifted early, but that is not the case, when it reaches that point, it just goes flat (doesn't rev anymore) you can hear the motor go sour.

Kevin91Z

The rev limiter is set to 6400, so its not hitting that. I think we are just hitting the limit of the horseshoe-shaped TPI runners. The intake manifold flows 315 cfm (up 55 cfm from 260 cfm) and the heads flow 260 cfm at 500" lift. The overal runner length of my siamesed SLP's is about 12-14", less than an LS1 at 17". But a TPI intake has huge curved runners while an LS1 has flat curved runners inside the plenum. I dont get it, as I dont understand the physics of air that well.

__________________
1991 Camaro Z28
355 RWHP, 360 RWTQ
12.803 @ 108.50 MPH (1.923 60')
Member: Southern California Thirdgenners
-=ICON Motorsports=-
Work: Manley Performance Products

1989GTATransAm

As you can see on Kevins motor the horsepower peaks around 5300 rpm and just flattens out. By the way his intake manifold flowed well past 300cfm. His SLP runners have had major surgery. Maybe only a couple of inches of runner left and a big plenum area. The question is why does the motor peak that early? Mine does the same thing.

As most of you know my car has had a new and larger cam installed and new valve springs with a much higher seat pressure. We should be putting it back on the dyno in a couple of weeks to see what happens. If it peaks at say 5300rpm and the horsepower flattens out again I will be totally perplexed. After seeing Kevins dyno run I'm afraid that is exactly what is going to happen.

This is why DynoDon is asking the question. We are looking for opinions as to why these motors are peaking so early horsepower wise.

Orr89RocZ

Do you feel the heads are a limiting factor? 260cfm at .500 lift aint bad, but could be higher to better match that intake.

What are the specs of the cam? Valve timing events with custom cams may need to be tried to keep pushing in more air at those higher rpms.

What you've done so far is very impressive. That flat power curve is nothing to sneeze at but i would think you would have enough flow and runner length to make more power over 5500 rpms. it seems 5500 is a kill point where no more power can be made. The theory of runner shape may have some real influence on how power is made. It could be disrupting the wave harmonics and preventing power being made up top.

Kevin91Z

My cam is a Lunati 226/232 with .580/.565" lift with 1.6 rockers and 113 LSA.

Orr89RocZ

I wonder if the much higher lift is hurting if the heads dont flow much more over .500 lift? I would guess the heads would be capable of holding peak flow around .550-.600. I just wonder if the extra lift is creating disturbances in teh air flow at those higher rpms. It doesnt look like valve float problems so that cant be it

I know since your in cali and need emissions, it be hard to try different cams. I'm wondering if that 113 lsa is hurting alittle on the top end and the motor wants abit more overlap, like a 110-111 lsa. Your duration is good to make peak power at around 5800 or so, maybe abit more.

I would guess its not doing so because of the possible shape of the runners with its u-shaped bend, or the cam timing events are not the best match for the intake design and its not pulling in the air like it would with a different manifold setup

Fast355

Have you'll disabled double fire mode on the injectors? The engine might run better in single fire mode, running longer pulsewidths for more fuel. Like asynch with a TBI setup.

Orr89RocZ

Good point, what sized injectors are you using and what is the cycle duty. I would think 30lbs are needed for that setup

Dyno Don

We are using 30# injectors running around 80% duty cycle, 46# psi, 12.8-13.2 AFR.
The 02 volts are @ 950-1000, it didn't like being leaner.

The actual flow on the heads is 266 in. at .550 202 ex. @ .550

Correction on the cam 226-234-113 intake centerline on 109*

Here is what the runners look like:

85gulstrandTA

I'm new here with 3rd Gen and with TPI stuff so forgive my ignorance. The way the charts drops off makes me wonder if the fuel flow is to the point the saftey switch is interupting the flow, or a limiter in the ECM, a long rubber fuel line being sucked closed, to narrow fuel line, fuel filter maxed out on flow. Just some thoughts I had. I was looking for a book that has some TPI information in it but I can not locate it yet. Cheers

Orr89RocZ

i dont think its a fuel issue if the air fuel ratio is staying good at those rpms. It sounds like its just not pulling in the air needed to make use of more fuel to make more power. its just not filling the cylinders

I want to say 266 cfm on the heads just isnt quite enough and better heads/port work to get flow in the 280 range is what is needed.

The cam looks good enough to make power in the 380whp range if only it kept climbing after 5300. The power was climbing good till the flatlining.

I'm thinking the shape of the runners is going to require a matching cam with valve events to work with the flow characteristics of those runners. Definately a head scratching case here. You have the flow, the cam and fuel to make the power its just not getting all of it

1989GTATransAm

Like was said above if the line on the dyno graph was carried out it looks like the motor would peak around 380rwhp in the 5800 to 6000rpm range. I suspect it has to do with something happening to the airflow. Just got to figure out what.

ploegi

Hhhhmmmm.... Looks like a mighty big vacuum leak there....

Ok, so the Base will flow 315 CFM. Have you tested the entire intake system for flow? What throttle body do you have on there? And what are you using for a filter? Is it possible that the intake tract BEFORE the throttle body is the weak link?

1989GTATransAm

Ploegi. Good ideas but he was getting 100kpa in the plenum throught out the dyno pull. That would indicate the plenum was at atmoshperic pressure or darn close. The air filters were pulled. So something is happening to the air between the plenum and the head.

ploegi

Figgered it would not be that easy. Any thoughts on flow for the whole intake system? As manifold pressure was good, my guess would be that we are not seeing a problem of flow-limiting intake.... which would have been my first thought..... How about the other end? (I have not checked out the other thread yet, will do so shortly....) Possible that it cant pump the exhaust out?

Orr89RocZ

i'm thinking its the runner shape. The air is doing something as it goes thru the whole system at high rpms, got to be something with the bend and harmonics, and i'm thinking the cam needs to be worked over to properly match that intake setup. Definately would like to see tighter lsa/more overlap, but i understand emissions is a concern

Zipdrive

you have enough air flow to support 440-ish hp at the heads and the runners. The biggest thing that I feel holding you back is the plenum volume. It is just too small, based on my experience. The next thing up line is the volume of air between the filter and the TB.

Since this would be for a dyno 'experiment', i would recommend cutting open the top of the plenum and welding on aluminum sheet to double or triple the internal plenum volume. Epoxy in a couple of horseshoe shapes in-front of each set of runners (try 1/2" tall) and shape them to 'look' at the plenum top.

The other crappy thing you will be fighting against is air in the 'extended' plenums. Instead of pulling from the common plenum, the air gets pulled back from the extended plenum and has twice the mass (volume) to react to based on the next cylinder firing. This will cause a 'sluggishness' in the flow vs. just a shorter runner and all connected by the same volume plenum. Increasing the plenum size will help this out.

You do have 1 and 3/4" headers, yes? I also believe that they are shorties? Long tubes would help with a tuned collector, but we live in the CRC. Hope that this helps.

1989GTATransAm

I was just over at DynoDon's and we were looking at the data logging. From all three cars on the dyno it looks like the dyno rpm numbers are reading 300rpm to low. Where Kevin's car was dropping off at 5800rpm on the dyno tach, the datalog shows it is around 6100rpm. Same with the other cars.

So if that is true he was starting to make peak power at 5600rpm. That puts things in a little better perspective as far as peak power goes.

Regarding the plenum volume it is extended well into the runners. There is nothing but a cover that goes over the runners as shown in the picture above. I figure on my setup I have extended the plenum volume by 50%.

Dyno Don

Also, we have another similar project using a SuperRam with the same results.
The power just flatlines after 5300.

His Graph:

Attached Images

John's Graph.jpg (69.6 KB, 173 views)

Zipdrive

I understand that the top half of the 'old runners' has been ported out to an empty volume that has increased the plenum volume.

But, you have created a 2nd-ary plenum where the runners were. To increase the original plenum, would lessen the effect of runner resonance to each other as the current state of design. They (the plenums) are acting like a pair of springs in series each with a different stiffness (k-factor).

Guys, what is the cross section dims of the open sections of the runner plenums? Any idea on the radius of the horseshoe section? For giggles, I would like to run some numbers.

1989GTATransAm

I understand exactly where you are comming from. That is one of the reasons I made mine a little different and opened it up more at the top by the plenum. All four holes are now one big hole to create a bigger chamber in that area.

A few things to think about. Normally the harmonic waves will change direction at the first open area. This is what occurs on a carburetor single plain intake manifold at the small plenum area. All eight ports empty into that area.

On our modified TPI system we have something quite different. Working back from the head we have two ports that empty into one now siamesed port. The siamesed port is now slighly bigger in area than the combined single ports because the divider wall is gone.

Then on Kevins the two remaining siamesed ports on each side open up into one big plenum area. Maybe a secondary one because of the way his entry area is constructed leading in from the main plenum.

One of my questions would be does the siamese runner area act like a plenum or does it act like just a bigger runner. If it acts like a runner that would make for some interesting harmonics. Now one would think the speed of the air in the siamese runner area would be slightly less than 1/2 the speed of the air in each individual runner.

That would set up two different harmonics. Maybe at a certain rpm it becomes a problem? The siamese area on my runners are longer than either Kevins or Dons and maybe has problems at another rpm range. My secondary plenum if you will is also different and I think less susceptable to harmonics and acts more like one big plenum in conjunction with the main plenum.

Now if the siamese runner area acts like a plenum there should not be a harmonic problem. Can't wait to get back on the dyno and see what happens.

Orr89RocZ

Definately look into that dyno and tach signal to make sure its getting an accurate rpm reading

TA

I think it would be interesting to drop a single-plane manifold and a 700CFM carb on the same engine and do dyno pulls. That would make absolutely certain that the intake system was the problem, and also set a bar of "expectations" to shoot for.

Finding a tuning problem is often a game of eliminating what is NOT the problem.

TA

Dyno Don

I don't want to quote all of that plenum and runner stuff, but do look at that last graph I posted. THAT was with a Super Ram and they look very similar, don't you guys agree?

Those are two different runners systems (one long & one short).

But they both flatline the power at 5300

Orr89RocZ

superram has a bigger plenum than a TPI, but its overall runner length is similar to the siamesed TPI setup that you tested. And with that siamesed runner setup, that should make the plenum area larger to mimic the superam

What was the cam used in that superam? that may have made a difference.

1989GTATransAm

The intake manifold itself could have been the limiting factor on the Super Ram. Was it not Extrude Honed? I bet it flowed a good 40 cfm less than Kevins. Maybe even 50 cfm.