poncho@home

Hey I just finished up siamesing my runners. Now all that's left is to clean them up and ceramic coat them. Here are some pics

Pic1
Pic2
Pic3

What do you all think?

bnoon

Have there been any dyno proven results of doing something like this to stock runners? I've seen the siamesed base numbers, but never just the small little flange area of the stock runners...

Did you match the plenum and base too???

ZFORCE

I thought "siamesing" was to take out the entire middle section between the two runners and weld covers on both sides to tie them completely togther?

Looks pretty good should net a few extra ponies.

tj

poncho@home

Not that I've seen any results, but I figured it was worth a try on a spare set of runners I picked up. It should have a similar effect as the siamesing of the base, maybe just less. Also the decreased runner length on top should help move the peak HP range up @200 rpm according to my calculations.

Actually siamesing is joining of the two adjoing tubes....how much of a siamese depends on the distance this is done for. I choose as a first step to try this mod out. Depending on the results I might try a full siamesing of the runners.

In total I shortened the overall runner length by @.9" including removing the plenum divider walls. I then added aproximately .4" cross section to the runners at the base. This should result in a peak hp roughly 200 rpm higher and overall more power...how much? probably neglible...but the results I have read about with siamesing the base seemed to net anywhere from 10-20 hp. I figure this might be good for overall 10 hp.

I am also installing 1.6 Roller Rockers. The way I figure it I might be able to gain anywhere from 10-45 hp from these mods...only results will tell. If I manage to get everything back on tomorrow, and the weather holds out, I will take it to the track. Otherwise hopefully we'll still get another weekend to try it out before winter rears its chilly head.

I will for sure make a run on the highway and see if I am flowing more air into my engine. How will I know you ask? Well one of the benefits of a Mass Air Flow system, coupled with Moates scanning software, I can see my MAF rate. I have my previous highest and will see if these mods yield a new high...it should.

benz28

From your pics, the siamese area looks like it has 90 degree turns. If you radius cut them, then the air flow should be better. That's what the purpose of shaving the little walls inside the plenum right before the entrance to the runners...the overall flow will be more efficient (this is only true if you have not done anything to your runners or your runners are not siamese.)

Why did you siamese the bottom end of the runners? Won't that cause turbulence within the intake manifold and runners? Just a thought.

rezinn

Why would you ceramic coat stock runners? You could probably get some aftermarket runners with meat on them for real siamesing for the cost of a good ceramic coating.

shawn87gta

iTrader: (1)

I don't want to rain on your parade but I doubt you'll see much from this. No flames intended or wanted, I am just sharing what I experienced myself. I siamesed the top entry my old SLP runners (& matched the plenum), after I had been running them as cast for a while, and it seemed like it pulled a little higher RPM's but that may have just been optimistic hope for all the work I did. I had already removed the EGR walls and opened the front of the plenum to match the 52mm tb prior to this, and ported the stock base intake to match the runner diameters and the head ports. I siamesed them much deeper than you were able to but at the top only. I think there's more potential at the bottom of the runners to allow the cylinder to pull air from more than one runner tube, which is what happens when you siamese the intake runner bores - you effectively create a secondary plenum area. I would limit the siamesing of the base to roughly a cross-sectional area equal to the diameter of the runner - in other words not very deep. I've read about people having issues with cylinders running lean when the intake is siamesed extensively. Siamesing too deep may also negatively affect air velocity, which is what "makes" the TPI. I also wonder what trade-off will occur as a result of turbulence - you may want to taper the siamesed area into a blade shape if possible to minimize turbulence. Please understand I am no expert in fluid dynamics or in TPI/FI motors so I could be entirely wrong. It will be interesting to see if you have good results with this and I wish you the best of luck with your efforts.

poncho@home

Not enough material on the stock runners to radius cut them.

To allow each intake valve to draw air from both runners...that's the theory behind siamesing the intake base. Oh and it might cause tubulace....I honestly don't know if this will work but that's what I am trying to ficure out.

I am ceramic coating them myself. No cost involved besides paint. BTW I wouldn't spend much money on stock runners before I bought aftermarket. Mind you I have read mixed experiences with SLPs.

You are not raining on my parade. I think its great to have varied points of view discussing topics like this.

I am trying to decrease the overall runner length like SLP did....I did some calculations for runner length and the "tuning" effect of velocity and reflective pulses and calculated that each 1" shorter will increase the RPM peak by 200-250 rpm on the 3rd pulse. That's what I am trying to do. According to my scans my MAF rate falls flat around 4600-4800 RPM, I am trying to get that to 4800-5000 RPM. See this link for quick results on runner length differences here

That's what I've done. I have effectively increased the cross section by .4" on the bottom of the runners. I did this to the runners because I have no intentions of cutting up my SDPC Vortec TPI base....simple as that. These are a second set of runners and plenum I am playing with. All my stock parts are on the side and untouched. Depending on the results I will either fully siamese these runners or move onto aftermarket runners.


All this to say is that I am not sure if this will help or hurt, but I figured it's worth a try!

Fevre

Not sure if the physics is the saem but I would imagine that is similar to adding an h pipe to a dual exhuast system. Wonder if having the runners cross like an x-pipe exhaust set up would net similar gains? Probably diff forces at work but still am curious......

1bad91Z

iTrader: (1)

The problem there lies in the diameter of the runner's tubes. You will not see any power gains in peak horsepower by doing that to stock diameter runners. You may however increase a few horsepower in the range of 4,900 - 5,100 (where the power has already died off). The numbers in that range may increase by 3 - 5 horsepower, but dont be expecting a seat of the pants increase!

You will however see a nice gain with a Larger tube diameter runner!

Good luck and let us know the results!

poncho@home

Will let's see...if the SDPC TPI baseplate only has 1.6" runners and the stock TPI runners has 1.47" runners, then obviously large tube runners would help.

My calculations say that 1.6" runners have a cross section of 2.01".

1.47" runners have a cross section of 1.69"

My siamesing has a cross section of roughly .3-.4" add that to the 1.69 you get 1.99-2.09" total cross section just before the lower intake runners.

While I agree that the increase may be neglible...in all honesty large tube runners probably wouldn't make more of a difference either...unless their is a negative impact from the actual siamesing, i.e .turbulance or imbalancing, time will tell. But the actual airflow should be equal, no?

bnoon

No. Cross section is a 2D flat area. Runners are tuned by volume and air speed together in a real world 3D port. Mathamatically, a larger hole = more CFM that would = more HP if volume were your only variable. Add in air speed and you just created two stall points in the ports...

Your slight increase in total volume, minus the fairly large air speed loss that you will see from the turbulence created will end up in a loss in performance at most RPM. I say *most* instead of *all* only because the turbulence *may* stumble across some sort of extreemly low RPM cylinder filling increase. Random merging of two ports is a no-no. But I guess we can use you as an example if it doesn't work...

poncho@home

The results I have seen from siamesing the base seems favorable. I haven't I done the same thing on a smaller scale?

I agree velocity is important, very important. I am not saying I am right but it's worth a try. Hopefully the added airflow can compensate more than the decreased velocity, if any.

By the way I didn't come up with this totally on my own, rather from lurking this and other boards and sifting through countless posts to determine accurate info. It seems alot of people recommend siamesing the intake for slightly modded engines. Seeing as I won't touch my intake the next logical step was to do the runners.

I also saw a page from a member that has done this and his SOTP dyno say he saw an improvement...it might have been related to other factors as well, I wasn't there to know for sure. Either way we will know soon enough.

Here is a link

The increased flow capabilities of the vortec heads, headers and exhaust need more intake air flow. I am also installing 1.6 Roller Rockers to help get more air in the cylinders along with the ported plenum and ported runners.

1bad91Z

iTrader: (1)

Ok, this is how it was explained to me a long time ago:

You want volume and velocity (as much as possible) to feed the heads. With that said, think about this......... If you open up the top side of the runner diameter, you get more volume. Then it bottlenecks torwards the middle of the runner tubes. Now, the air is traveling at a smaller diameter. If it continues at that smaller diameter, it will maintain velocity. If the bottom side of runner is then opened, not only will the volume stay the same, but it will decrease the velocity, hence loosing power and the "tuned" effect.

So, the Idea is to get larger diameter tubes to flow more volume and maintain velocity.

Now, this is what SLP told me! Also, SLP told me to NEVER siamese the upper plenum. The engineer there told me to radius the openings to match the bigger gaskets, but do NOT knock out the tube divider walls on the upper plenum. Doing so will cause un-even air distribution (throwing more air to the back tubes of the runners < cylinder number's 4 , 8 , 3, 7 > would recieve more air than the other cylinders).

Now, I may have been mis-informed, but the engineers at SLP are there doing what they do there for a reason!

Just my $.02

poncho@home

I read this from you before it all honestly doesn't sit right with me. The runners are drawing air from the plenum not being forced air from the TB.....I can see it if the air was being charged into the intake but that's not the case...when an intake valve opens it draws air in from the plenum so I can't see why removing those walls would have a negative impact. BTW I am by no means a engineer....just visualising what's happening in the intake. The SLP has changed over the years by the way. At 1 point the runners had 1 set of tubes completely siamesed and the other as they are now, then at one point both only part siamese at the top. Why the change? Any ideas?

I do agree with you for the bottom of the runners, I'm just hoping the good will outweigh the bad!

1bad91Z

iTrader: (1)

Ok, here;s my take on that:

Full siamesed runners - this decreases the runner length by the full length of the runners effectively make the plenum area larger. These runners were smaller in overal diameter per tube wise. But this design increased horsepower and a bigger sacrifice of torque than the new design.

Semi-siamesed runners - this reduced overall runner length by a smaller percentage than the fully siamesed ones, but they slightly enlarged the diameter of the tubes which not only yields more horsepower, but maintains the torque that old design lost.

Jed

Ok, I have to ask...if you have so much faith in the SLP engineers design, why have you (and many other people who have SLP runners) changed the design of your SLP runners by extensively porting them?

Because you knew you'd see a performance gain if you did it, right? But I doubt SLP would encourage you to modify their runners. If they did, they would be admitting that the design of their runners is lacking, and that there is plenty of room for improvement.

They may just tell people not to siamese the plenum for liability reasons.

If what the SLP engineer told you was really true, then this setup wouldn't work well at all.



However, this setup has been proven by several board members. With the siamesed plenum.

TPIgirl

I hope it works out for you and me both because I'm porting on mine too while I wait for my heads to be done.





Oh yeah and I am making my own gaskets from a sheet of cork.

89blackGTA

What runners are those?

Brian

llvll4l2c91350

looks like you cut too much off. i dont see how any gasket would seal right.

Jed

Brian, they are Arizona Speed & Marine semi siamesed LTR's.

TPIgirl.... is there a BIG chunk missing from the top of that lower intake, or am I looking at that picture wrong?

onebinky

iTrader: (1)

I was playing around with that program in the link, and the results I got are listed like this:

For 2nd harmonic, RPM range is from 4699 to 5702 with a pulse strength of 10 percent
For 3rd harmonic, RPM range is from 3531 to 4035 with a pulse strength of 7 percent
For 4th harmonic, RPM range is from 2753 to 3078 with a pulse strength of 4 percent

What does the harmonics and pulse strength mean?

Matt

poncho@home

Harmonics is the actual air charge rushing down the runners. Because air moves at near the speed of sound and the valve only opens for a certain amount of duration per cycle the air charge needs to travel a few feet to be at the valve at the time it opens. Since it is only travelling aroiund 21" in our case it hits the back of the vavle and returns up the runner to the plenum back and forth, thus leading us to pulse strength. The more times it has to bounce back ansd forth down the runners the weaker the strength of the charge becomes.

By my caclulations each 1" shorter runner will result in increasing the 3rd harmonic by roughly 200 rpm in a stock TPI system. Thus the tuning effect of the TPI will occur 200 rpm higher. All the aftermarket runners are shorter in design as well along with larger diameter tubes. I am hoping that the bottom siamese will add the extra a volume I need and still maintain good velocity.

TPI Girl....how are you going to seal the runners to the base....looks like you went to far, no?

onebinky

iTrader: (1)

Thats some interesting info. Thanks Poncho

TPIgirl

I'm not finished with the intake yet. I'm just raising and flattening the roof. I'll post a pic when I'm done.

shawn87gta

iTrader: (1)

TPIGIRL, I see the same thing in those pics - the sealing surface has been partially removed. Do you plan to weld material over the top of that runner then mill it back? I assume that's what you mean by saying you are raising & flattening the roof. By the way, thumbs up for doing this sort of stuff yourself. Most of the women I know could care less about cars, much less be willing to work on them as a hobby.

Other than where she removed the sealing area, what she's done to the opening here is what I did to my SLP runners. I just opened them up as far as I could reach with the bit and put a nice bevel on the divider wall. I siamesed the plenum to match. My theory was that I was both increasing plenum volume and shortening the runner tubes, "detuning" a little. I did feel the power band move up in rpms a little and the engine pulled a little higher. I was able to wind it pretty hard to ~5400 before it would seem to plateau. Poncho, let us know how your results turn out.

TPIgirl

I'm just going to use some epoxy to form the roof and make gaskets to fit it.