Recently i aquired an 86 trans am with TPI. After studying the TPI intake ive discovered alot of things i do and do not like about it. Now the concept of how TPI works with its long runners so the pressure pulses hit the valve conveniantly when the valves are opening is i think great. Even though this system is more geared twords low end torque and economy i think its a great concept for a street motor. However i think the execution is not allowing this system to live up to its full potential for several reasons.

1. Excessive snakeing of the intake through the runners/intake and into the head.

2. Lack of tapered runners.

3. Thin long thin walled aluminum runners i believe transefer heat too well to the intake mixture.

4. Runner diameter is insufficient for larger SBCs

5. Runner leingth although still remaining a long tube runner set up could be better tuned for more mid range.

6. fuel injector locating good but could be improved

7. Possability of adding a variable intake design to yeild both low end torque and high hpm performance

Now because of all this I decided to look into aftermarket solutions however due to cost and some of the same fundamentle flaws ive decided to look into fabricating my own sheet metal TPI intake. The advantages i think would be one of the best street TPI intakes that could be produced with some R&D work at a much reduced cost by any enthusiest with some fabrication skills. Now im pretty well versed in fabricating things so my point is not so much how to do it but more i want to hear about some input from anyone about things they would like to see other improvments not mentioned or ways to figure out what kind of runner volumes or taper rates plenium shapes or any theory of intake manifold design you have to offer. Right now i have a few basic designs im tinkering with but again i need to figure out the details to proceed.

 

Look at our sticky post in the TPI forum "Quest for a better flowing TPI." You'll find the trials and experiments with different intakes on my engine. Along with our theory and ideas. You can also search the TPI forum for "siamesed SLP runners" to see how they were built, and search for "Visual TPI intake ports" for the pinch points we found in the TPI lower intake manifold.

 

thats funny i was just thinking the same thing i was thinking of making the fuel rails longer and the middle of the manifold taller to allow more air also moving the egr to the passenger side


my 2 cents

 

the improvements you are looking for were progressively addressed in the LT1 and then the LS1 intake manifold. LT1 manifold staps aren't that difficult and get you part of the way there.

 

Well yes and no. The LT1 intakes are more of a short runner design or atleast a shorter runner design. Better for high end hp but im more looking to maintain a long runner design to emphisize the low end torque and economy. The LS1 intake has yet an even shorter runners. Now the catch of long runner vs short runner could be addressed with a variable intake manifold design which was not incorperated in eather of the designs. Although befor i start anything i need to do alittle bit more reasurch into the math and physics behind it all.

 

I could've sworn LS1 runners were longer than LT1 runners, but i don't remember the lengths. you might wanna check that again.

 

you are right ls1 runners are longer


im thinking about cutting the bottom off my manifold and welding a deeper bottom to help with the choke points

 

Oh i was under the impression LS1 runners were shorter than the LT1s eather way it kinda confirms my thoughs on haveing runners on the longer side. I mean ive got alot of numbers to crunch on this one but there are a few fundamentle things that seems i have to account for.

1 Plenium volume
2 runner leingth and diameter
3 runner taper
4 injector location and angle
5 how to most effectivly implament a variable manifold design
6 Reducing the snakeing through the intake to the cylinder head improveing flow without increaseing diameter

Now i dont want to say too much yet as i havnt really worked through all the numbers and physics yet but so far from what ive crunched out it seems one of the best choices i think will end up being abandon the factory stuff and use the basic concepts to fabricate a dual plenium set up. Now im not sure exactly in what configuration yet as i few ideas i have to play with first, still it seems like solution that could work and solve some of the factories short fallings.

 

i think its best to stick with the factory plenuem and runners as those are most available and make a different base

 

Well the problem is i mean the base is far from ideal with out question but to really solve some of the fundamental issues i see its not just in the base. Further more the concept of having a base runners and a plenium in seperate pieces isnt really neccessary. It is in the factory design but not neccessarily has to be. With just fabricating a base there wouldnt be much hope of integrating a variable manifold design. The runner leingths and plenium volumes couldnt be fined tuned. Idk to go just half way it just wouldnt make sence to do it at all as there are some bases with alittle work will work pretty nicely.

 

Intake Runner lengths

21" TPI
3" LT1
15" LS1

Head intake runner lengths

3" TPI/LT1
5" LS1

http://www.popularhotrodding.com/tec.../photo_09.html
http://www.smokemup.com/tech/ls1.php

You need more research before beginning this project

 

What about taking a ls1 intake and transplating it to a l98 I know it won't fit but
If its going to be custom it will

Make it using the oem throttle body so all the stock superchargers still work?

 

there is really no making it fit since the arrangement of the intake valves is completely different.

Rolling Thunder- You keep bringing up the idea of a Variable Intake Design/ Variable Manifold Design. Can you describe what you mean by this?

 

Certantly i will gladly discuss the variable intake design. Now we all know for the most part runner leingth is important and long tube runners tend to favor low end torque and short runners tend to favor high end hp now the problem is having to chose between the two and find a balance. However this is weher the variable intake desing comes into play. Essentially its like haveing 2 sets of runners a short set and a long set and switching between the sets or useing vacuum to find a balance betwen the two to effectivly create a variable runner leingth. With this we wouldnt have to chose between high end hp and low end torque, drivability and economy. This concept is in use today on motors and can be explained further in the link below.

http://www.autozine.org/technical_sc...h_engine_2.htm

to rock861261, at this point more than likely it will use some kind of dual plenium so even though ill probably use some kind of factory throttle body it is unlikely that it will be just a bolt on replacement for use on a super chargers designed for factory TPI system. That being said i dont think it would be so radically different that it cannot be made to work but would deffinetly require a good deal of modifications.

 

Not really. The LS1 doesnt really take any less turns, it just does a lot better job of minimizing the transition changes. If you look at your intake again, you'll notice that GM spent zero effort on making the direction of the airflow in one piece match with the airflow in the next.

IMO pointless. The area where that is of most concern is going to be at the valve. Who cares what it does before then.

Run a open cage rather than solid brass IAT and check that theory. That isnt the case. A full composite intake wouldnt hurt, but you're talking about a lot of effort and expense for little return.

Quite true.

Thats why there is the Super Ram, the T-Ram, and the Stealth Ram.

Pointless. The firing strategy of the system means that most of the time, 7 of the 8 cylinders (and maybe all 8) fire the injectors at closed valves in a stagnant airflow path. TPI is batch fired, all 8 at once. Maybe if you converted to a sequential fire this would be something to explore.

Speed costs money, how fast do you want to go?

 

Originally Posted by Rolling Thunder
1. Excessive snakeing of the intake through the runners/intake and into the head.

Not really. The LS1 doesnt really take any less turns, it just does a lot better job of minimizing the transition changes. If you look at your intake again, you'll notice that GM spent zero effort on making the direction of the airflow in one piece match with the airflow in the next.

Yes the LS1 intake is an improvement but the factory TIP intake could be much improved with a better design

Quote:
Originally Posted by Rolling Thunder
2. Lack of tapered runners.

IMO pointless. The area where that is of most concern is going to be at the valve. Who cares what it does before then.

Tapered runners actually do have a bit of an effect for 2 reason one velocity can be improved befor it even reaches the head and natrally when air is flowing through a runner there is a pressure drop related to leingth. This can be compensated for with the use of tapered runners. How much of an effect these factors would have isnt really known at this point as more numbers still need to be crunched but it would help reguardless.

Quote:
Originally Posted by Rolling Thunder
3. Thin long thin walled aluminum runners i believe transefer heat too well to the intake mixture.

Run a open cage rather than solid brass IAT and check that theory. That isnt the case. A full composite intake wouldnt hurt, but you're talking about a lot of effort and expense for little return.

Aluminum transferes heat very well thats one of the reasons why there used to make radiators. Now the surface area of individual runners is quite large when compared to other even factory bolt in replacements. Now how much it would help to insulate them is unknown at this point but the runners would not need to be made of a composite material to insulate them. It could be done as simply as painitng them as paint does not transfer heat well. Although for the effort i would look for alittle more than paint.


Quote:
Originally Posted by Rolling Thunder
4. Runner diameter is insufficient for larger SBCs

Quite true.


Quote:
Originally Posted by Rolling Thunder
5. Runner leingth although still remaining a long tube runner set up could be better tuned for more mid range.

Thats why there is the Super Ram, the T-Ram, and the Stealth Ram.

This is true but again i would be able to tune it to the range i want rather than use the set ups they have that are designed to work in a variety of applications. Plus again they dont really encoperate any of the other things i would like to see.

Quote:
Originally Posted by Rolling Thunder
6. fuel injector locating good but could be improved

Pointless. The firing strategy of the system means that most of the time, 7 of the 8 cylinders (and maybe all 8) fire the injectors at closed valves in a stagnant airflow path. TPI is batch fired, all 8 at once. Maybe if you converted to a sequential fire this would be something to explore.

This is true however the fuel injectors could still be placed better as the should be placed at the point of highest air velocity. Even though the valve is probably closed when the injector fires the valve will open at some point and it should be at the point of highest velocity. In the factory system i do not believe they are in an ideal location even for a factory set up and with tapered runners the air velocity could be improved for better atomization. The injectors could also be moved closer to the head and angled differently again for better atomization.

Quote:
Originally Posted by Rolling Thunder
7. Possability of adding a variable intake design to yeild both low end torque and high hpm performance

Speed costs money, how fast do you want to go?

Concidering that i will be fabricating this in my free time the additional cost would be minimal or non-exsistant. If i was going to have to pay someone by the hour to produce this than yes but fortunetly im not. Concidering the gains it would be well worth the effort as well.

 

You might spend your time better on the injectors updating to the new Bosch Type III design that atomize the fuel much better than the injectors these cars used. That will help more than idealizing the injector angle.

Aluminum in itself isnt the best heat conductor. It is better than cast iron, thats why you can and should run higher compression with AL heads because they bleed more heat from the chamber. But that is not why they use it for radiators, brass and copper do a much better job of conducting heat to the air, aluminum is just lighter and better for construction purposes. I think if you check intake air temps with an open element sensor so you see the actual air temps in the intake you might find that once the air is flowing at a decent rate, the amount of heat transferred is not much. The only reason a scan tool shows IAT's in the 110ish range on a running engine is because the sensor is completely closed and the brass is heating up to the temp of the manifold, not the air thats in it. If you're going to fab up a composite intake anyway, I wont stop you but if you're going to do it for IAT reasons alone, its way too much cost and effort for too little result.

 

if need a serious intake, y not look into a efi vic jr. with a 90 degree elbow, with a ls1 tb. or a sullivan elbow which can adapt to use a twin bore 58mm or mono blade tb?

i would have to upgrade the heads to standard sbc as well.
no oem tpi heads will ever move enuff air to warrant such r&d. not even l98's ported by a very good porter. the afr's are good heads, but the oem tpi intake/heads just not all that great for a serious n/a perfomer.

 

Well converting over to bosch type 3 injectors may be someting to add into the design but reguardless anything that can be done to improve the basic design would help. Now your also right that the IAT temps according to the computer is about 110. Ive measured under hood temperatures of upwards of 150 with headers. However with a good cold air intake your taking in air significantly cooler than eather of the figures. Say for example you were running a speed dencity type set up and you had the intake of the TPI directly plummed to a hood scoop the IAT would be the outside temperature plus whatever effect heat soak has. Now depending on rate of flow and the rate at which heat can be transfered depends how much effect this has but if outside temps are 60-70 and underhood temps are ~150 theres a fair potential for heat soak to occure. Now with added insulation weather it be an insulative coting or composite material i believe it would help noticably. Granted this is not the sole factor of why im taking on this project but its another short comming of the factory system that should be attended to in a revised design. I will have to say though aluminum is a pretty good conductor of heat. It is deffinetly better than cast iron but it is also significantly better than copper and brass tubing. It is light weight which is another advantage but it transfers heat pretty well.

 

Well the objective is not so much to have a serious intake just a smarter one. In other words look at heads for a moment and what is the difference between a good head and a bad head. If you have a head with an intake runner that can flow 200 cfm out of a 180 cc runner and another that can flow 200 cfm at the same valve lift out of a 200 cc runner assuming standard testing condidtions what is the better head if they flow the same? The 180 cc by far because even though the flow rate is the same the velocities are higher. So basically to improve the flow you have to increase the volume or the efficiency at which it will flow i hope to improve on the latter. So the idea its not so much to create a more serious performer but makeing a more efficient design to get flow from less volume. By doing this it will give better performance better economy better throttle responce better everything because its simply a better design. From there the geometry can be modified to fit performance requirements of different set ups and do it much more efficiently than a factory design. Now granted like you mentioned theres other things besiced the intake to concider but one step at a time lol.

 

I can tell you what the 93-97 F-body owners are doing.

The guys that own 500+ RWHP N/A 93-97 LT1 engines usually go with a ported Edelbrock SuperVic thats converted to EFI, its the best single plane intake out there for 23 degree heads. Ported Holley Stealth Rams converted to work with LT1 heads are looking to be the next best thing under them but not enough testing has been done yet to be sure. The ported HSR's are available in 3 stages of porting by the guy who's porting/converting them.

 

Well something like tha would be a great solution to build a max performance motor but i dont think it would work out too well for a a street motor. Not to say that its not streetable neccessarily but the edelbrock super victory manifold is designed for high RPM operation. This is because the runners are larger and relitivly short. What this accomplishes is huge potential for airflow in the high RPMs but in the low RPMs would have terrable air velocities which would lead to driveability issues on a street car. The other parts needed to match a intake like that would also put it out of the street driven catagory pretty much completely. The holley stealth ram on the other hand i think would be another fair choice. Its cheap flows pretty well it does take care of alot of the factory TPIs issues. Still though its more of a 2000-6000 RPM kinda intake where as im trying to design something more for the low end. Good suggestions none the less and i welcome any input any one has to offer. Especially if anyone knows anything about the physics of how runner leingth/diameter and plenium volume relates to a motor of a given displacement with a peek effecency RPM in mind. Or again any input on things people would like to see or dont want to see in a revised design.

 

If that were true then any LT1 car would run like poo
Powerband has very little to do with being streetable

 

There is nothing wrong with the LT1 motor. I know i said useing the large short runners makes the air velocities decrease causeing poor driveability but although the runners are relitivly short there runner volume is not really large its appropriate for a SBC to maintain good velocity and emphisize higher RPM performance. The edelbrock super victory on the other hand also has short runners similar to the lt1 but the runner volume is a good deal larger making it a poor choice for low RPM performance and will likely cause driveability issues. So how is any of that not true? Air velocities are key to fuel atomization and useing a intake manifold like the edelbrock super victory that is designed to operate in the 3500 + RPMs is not going to do very well in the low RPMs. I mean even when you look at what a power band fundamently is its a range of RPMs where the motor operates most efficiently produceing more power in that range. Running out side of that range may work but at a much lower efficency. Further more the motors power band has very much to do with streetability. Granted im not trying to claim that you cannot drive a car on the street that is designed to run in the 2500 - 6500 range or even one thats designed to run and even more aggrssive range like 4000 + but you have to concider just becasue it is moveing under its own power does that make it a good choice for the street? Case in point i knew a gentleman who ran a edelbrock super victory or victory jr on his street 305 and sure he drove it but was about as bad as it gets for driveability. For one the low air velocities caused the car to bog and hesitate in the lower RPMs below say 3-4 k because at that point the fuel actually has a tendency to form droplets rather than atomize. The lack of a exhaust crossover which is encorporated into just about every serious performance manifold caused it to run extremely poorly in the cold weather. The cam did not allow for things like power brakes to work. The torque to get off from a stop light was absolutly abserd. He was also forced to run a very high stall converter which meant his trans hardly ever locked up which caused some trans over heating issues that needed to be dealt with. The fuel economy was terrable. The steep grears made it scream away even in regular driveing and was terrable on the highway. I could go on for days about how poorly this power band was chosen for a street car but i think you get the picture. No you might claim that that is an exception and that is pretty extreme but when you look at even more tame set ups you see the general trend for sacraficeing low end toruqe for high end hp. Now although you may not thing giveing up 25-50 foot lbs is a big deal but keep in mind this difference is multiplied out by the gearing and if you do the math even something so small as a 25-50 loss turns out to be a large loss of thrust at the wheels. Even further more the power band is important because in a street car because most of the time is spent in the low RPMs and alot of these more radical set ups only outperform there tamer equivalent in the high RPMs. For a street cat this dosnt really do anything good for you as your highly ever there. Even further a typical sbc has a rev limit of about 5.5 k so building power over this limit is just a waist. Looking at cams for a moment they also are tied to RPM performance and attidute of the car over all and will only perform well over a certant band. A cam with a high RPM power band in the low RPM is going to cause all kinds of revertions into the intake, fuel can actually be sucked out into the exhause due to the large amount of duration and overlap, poor cylinder filling, dynamic compression suffers, again i can go on for days but it should be clearly obvious that one of the reasons the reason large cammed cars have that distintive sound is because they are running rough/poorly in the low RPMs. Throttle responce is again tied to air velocities and as flow rates are increased for a given size motor low RPM velocities decrease along with throttle responce. So to say that power band has little to do with streetability just dosnt make sence. From the stand point of can the car physically move under its own power on the street than ok just about anythin can be streetable but that dosnt make it a smart choice or reasonable to do so.

 

so your goal is to have better running, feels stronger, flows a lil better.
a overhaul of the engine with slightly more, scr, and a basic valve job, with some clean up of the heads, will prolly make the most noticeable gains youre looking for, i doubt just some light work or fabricated runners will produce any staggering results from just the manifold revision. its not just the runners hindering perfomance, the plenum itself needs some work as well, along with the tb, tb port size. etc. and the heads etc.
u will also have to adress exhaust scavenging since the factory manifolds, and exhaust do not help at all for perf. and further hinder any improvents made to the induction side.

 

Yea youve got the right idea. The way i see it lots has to be done. heads cam exhaust the works. Although this will be a big project i dont see any real reason for it to be too costly as its going to be fabricated on my own time from just raw materials. It will be pretty time consumeing but would be a good deal cheaper than an aftermarket set up. You can argue that its not worth the time and effort but i believe it would be a worth while project as i feel i can make some substantial improvements and i enjoy doing this kinda stuff anyways. Right not im focaseing on the intake because the theorys behind how the stock one works are pretty sound but the execution is kinda poor. With a better basic desing so much more could be achieved. Ive pretty much given up on useing factory stuff all together (except some kind of factory throttle body). I think the runner leing is up to debat how long it should be thats really a matter of application runner diameter is dependent on again displacement and RPM range and the plenium as well. So far from what ive gathered it would seem that the factory plenium is too small volume wise the runners although ok for a 305 not so good for larger motors and the leinth of the runners again is open to debate so i wont say that there bad persay. Further more i think the basic design just could have been a bit better layed out. Gm didnt do a bad job but when you have to design stuff with production economics emmissions so on and so forth they did the best they could. With a revised design though i think it would do much better and then the geometry could be modified to talor it to a specific application and power band. For my perposes i think a great low end emphisis would be nice so thats what im going for but again once the relationship beteen displacement and power band to plenium volume runner leingth and diameter is known the basic design could be modified for any application. So really what i hope to accomplish is not some much a specific power increase but to come up with a stong basic design for a new style TPI intake and be able to mathamatically predict what the dimentions should be for a given application. From there its a matter of testing trial and error but im looking to get a good plan together befor i wouch anything as it will be just doomed to failure without a good plan ahead of time. In my case im just looking to build a nice street manifold but even at that rate i think the gains would be relitivly substantial. Maby dollar for dollar not as good as many other mods but i feel its the achillies heel right now and needs to be tended to reguardless. Again many other aspects need to be taken into account to match but for this thread im just focased on the intake.

 

I don't know how much research you have done on this forum regarding modifying the TPI intake system but there is quite a bit of information and results. I would take a hard look at the dimensions of the LSX style intake system. IMHO it is an updated version of the TPI.

Another route is to get a program like PipeMax that is relatively inexpensive and will provide the dimensions you will need for both the intake and exhaust systems. Here are a couple of thoughts.

1. Regarding the plenum there are examples on this forum on how to extend the volume into what was the runners. But first of all you need to know how much plenum you are going to need. Generally it is the cubic inches of the motor. I don't see a problem with modifying the factory plenum for your needs.

2. The runners are going to be the key area in your design. The CSA, length and taper are the keys. As said above you can use part of what was the runner to increase the plenum volume.

3. I believe the First TPI intake manifold itself to be the best thing out there. It would not take much work to make it do whatever you want. If you are making your own runners you can make them match the factory plenum and the First TPI intake manifold.

 

Well the thing is i could probably do alot with a factory set up if i really threw some time and reasurch at it but another thing i want to accomplish is adding a variable manifold design which although possable on a factory set up quite a bit more complicated. As far as the plenium ive read threads about siamesing the runners to effectivly become part of the plenium improveing the plenium volume but without knowing what the plenium volume should be in the first place whos to know if its enough or even possable if its too much? So i need to come up with some equations relating the plenium volume to the displacement. Also the trade off is shortened runners which may or may not be a good thing again more numbers have to be cruched befor i can get a good picture of what i should shoot for. The FIRST base i have no real experiance with so i cant really comment on it beond what ive seen in dyno results although I agree for a street car the FIRST system as a whole is about the best ive seen hands down in my oppinion anyways. Of course i think with a new design it could possably be done even better. Lots of work but i think a fun project and who know i might hit on something pretty good. Ill have to check out that PipeMax program never heard of it befor but sounds like something i could use. Its one of thoes projects go all the way or dont even bother.