TheSamba.com :: View topic - tunnel-ram

Wed Aug 18, 2010 4:31 pm

Anyone else running a tunnel-ram or these primarily for sandrails and off-road? I,m having tuning issues. I'm installing a new Holley 4412 500cfm tomorrow. Hopefully this will cure what ails it. :wink: I was just wondering if anybody has been down this road. Yea I know......run dual webers,kads,etc.....I'm running Holley. If I have to, I'll run dual Holleys.....I like Holleys 8) !

Wed Aug 18, 2010 10:12 pm

You have a tunnel ram? You have to post some pictures!! I would love to see this. I am building a tunnel ram style intake for my project. its a turbocharged EFI and I am curious.

I know LOTS of people would tell me I'm stupid for saying this but... I thing that webers are ok but I.R. style carbs have down falls and could be better with a joined style plenum intake like a WRX. All nay sayers Please do not flood this thread with how awesome webers are. I am just trying to work outside the box and break the 30+ year old mold.

I am VERY curious to see this. :D

Wed Aug 18, 2010 11:23 pm

Not a nay-sayer.....I'm pro experimenter. I think your really talking about long runner intakes rather than tunnel rams. A short manifold Kad is more of a tunnel ram which typically is a short high volume plenum and port ram for high RPM (yeah I know the Kads are small diameter small plenum but the fit the model better).
Just to point in the right direction.....
A long small diameter runner will make great torque while the same length with larger diameter will make great mid-range and shorter large diameter will make great top range. It all has to be balanced and tuned to the heads and cam used. Of course plenum volume is also used to tune the whole thing as well. Typically, richer settings need to be used with larger plenums and runners so your Holley might require quite a bit of tailoring including the air bleeds which are not adjustable from the factory. When you get a the jetting rich enough to feed the transition it may be too fat on the top end due to small air bleeds. the jet and bleed are used to balance the fuel curve over the RPM range.
I like Holleys too since I have YEARS of prior experience with them. They are not easy to tune for a NA VW engine but with patience it can be done. Hail to the experimenters.
Can't wait to see some positive results.

RC

Thu Aug 19, 2010 10:45 am

Its a common misconception that tunnel rams are high RPM only. We have run tunnel rams on big and small blocks and compared to a single plane dominator it carries the same top end power but makes alot more low end torque by helping cylinder fill.

I'm planning on making an intake like this. This is a magnus intake for a 2.5L WRX STI. It makes 35hp over the stock intake. witch the stock intake is descent piece itself. turbos like plenum so I figure it should be ALOT better than stock 1600dp intake and end castings that so many people run. after all you wouldn't run a stock intake on a N/A 2332 so why on a turbo 2332?

Thu Aug 19, 2010 11:33 am

well I always ran a tunnel ram with 2 835 cfm hollys on my 13.8 to 1cr 340 full roller mopar I loved it & will probly never go back to a single carb. but if I knew what I know now about IR systems I would of made another top (IR) and got a set of 1150 domniators and ran it that way. an IR system makes so much more torque, and makes a killer cam idle smooth. an old friend came down from ohio this week trying to get my fully show polished ram assy for his street car & trying to trade a new in the box holly ram with $$ for it .but I allready have 2 of the holly rams & I will probably be barried with my weiand. I made a lot of $$$$$ with that street racing. If I were you I would runn the hollys but make it an IR system. I did run a single holly on my bug for about a year,but the sonic air wave makes a pinging sound at certin rpms that drove me nuts for months till I figured out that it wasent detonation, but sonic implosions in the intake. I think if you want to make a torque monster use the newer twin tube (mexican type) intake and put a single 4 on it IR or possiably a small well desigined plenimun. but for now on my bug the duel 44 IDF works great. but I have BP intakes on this 2028 &2"taller CB big beef intakes witch are not cast big enough for porting as they are addvertized ,on my 2332. I need to make some 2" Intake spacers to go under the bug poop intakes.witch are about 1" taller than my empi intakes I had on my 1874 cc. motor. so yes longer is better if they are made right.(and you can match the length to the cam & heads for some awassom suppercharging effect.

Thu Aug 19, 2010 1:22 pm

I have a offy tunnel ram for a 440 with carbs and stacks. know anyone interested? selling cheap going to EFI. got a 3" S400 turbo waiting for that. :twisted:

Thu Aug 19, 2010 2:26 pm

So if I.R. setups are better than why is it you don't see them more often?

Thu Aug 19, 2010 3:40 pm

That setup wont work on a Type 1 but good luck. :D

Thu Aug 19, 2010 3:54 pm

jesus_chrysler wrote: So if I.R. setups are better than why is it you don't see them more often?

Probably coz it doesn't fit the old school mentality of most American V8 builders. The original GT-40 had the Weber IR setup (as I recall). I think Shelby used it too on some cars. It was real common in Can-Am cars. The big question in those cases was top raw HP numbers.....like drag racing.....or drivability on a road course. I give drivability my vote every time.

Thu Aug 19, 2010 7:02 pm

Care to elaborate some reasons jimmy. works on other opposed engines quite well.

From what I have seen I.R. setups are more top end HP minded on N/A engines. Keep in mind I am going boosted. thats why am leaning to a plenum. I am open minded though.

Thu Aug 19, 2010 7:36 pm

A tunnel ram is a V-8 manifold, two carbs and a "tunnel" between them!
I don't know WTF you'r talking about with a vw tunnel ram.
Where's the tunnel?

A "power box" manifold is a carbed small plenum with long runners.
Is that what we're talking about?

Thu Aug 19, 2010 8:05 pm

IIRC back in the early to mid 90's, I think it was Ron Lummus, fabbed up a "tunnel ram" manifold using a Holley 4 barrel carb for drag racing. Keep in mind this unit was strictly for drag racing as there was no room for the original cooling tin and generator/alternator. I never really looked into that intake design at that time as I was deadlocked on using IDA's. But to look at the current scope of things, it looks like it never took off, as most are still using the standard IDA, IDF, DRLA, etc... for the N/A stuff.

Thu Aug 19, 2010 9:19 pm

From my experience on my car, going from ITB's to a single throttle body with a longer intake runner increased my low rpm power, but seat of the pants tells me I am not making the same amount of power up top. Maybe I am, but with no track time to back it up, I can definitly say it doesn't feel like more.

For reference, our atmosphere here is 84kpa. With my ITB's my manifold pressure maxed out at 91kpa @ 7500rpm. With my new single throttle body setup I am peaking at 87-88kpa so far.

From what I am seeing, for peak HP, ITB's dominate, but low end power is better with the other.

Thu Aug 19, 2010 9:22 pm

Modok there is a picture of exactly what I am talking about previously posted. You can call it what ever you want but the picture describes it better than words.

I was kinda hoping the OP would come back with some pics of his setup. I'm curious.

Thank you Eaallred. that is exactly the info I was looking for. You think it might feel not as fast cause it doesn't have the top end "hit" like it used to? Would you mind sharing some pictures?

Thu Aug 19, 2010 10:05 pm

Ok, you mean that subi one. That would be neat, hard to fit that with a fanshroud on top but I like the idea.
I suppose you could call that a "tunnel" since they stretched the plenum out to shorten the runners.

I thought we were talking carb manifolds.
Jimmy111 probably meant that's not going to work with a carb. I feel the same.

Wed Aug 25, 2010 6:04 pm

I basically copied the idea of the 4barrel version but I used tubing instead of the big awkward box. See my photos @ lovin' my w140 in the beetle forum. I'll get better pics of the intake later but you'll get the picture. It actually runs really good. Comes on @ about 3000 like a lightswitch(not too bad down low) and runs hard to 7000. I like it. It was just experimental and it looks bad-ass hangin' through the hood. Have to post more pics. It'll be painted this weekend. 8)