Hey all, I'm looking at trying Ram Tubes or velocity stacks as some people call them on my 2tg next race. But theres a few different styles... I'm just wanting your opinion on what you think the best option is. It's only bitumen work so i don't plan on running filters either. Cheers

The ones attached to the carb would look like they'd suck the most air and look the coolest!

Velocity stacks is just that..... They help to make the power in a certain rev range - long stacks = low rev power / short stacks = high rev power. But you'll only really get the most from them if their matched with the cam/s as well (not a good idea matching a long stack with a cam that makes the power high in the rev range).

 

But it also comes down to how much room you have as well

yeah i knew about the Long=torque short=revs bit.

I have maybe 100mm TOPS if I'm lucky, i was thinking 50-60mm long with at least a 60mm flange which then goes down to 40mm to suit the carbs I'm running. Keep your opinions and suggestions coming :P

 

Cheers

Apparently most the air flows from the sides of the bell mouth and a full wrap around radius like the ones attached to the carby flow the best.

yeah i was talking to a bloke at my local car club and he said the same thing about the air flows in from the sides. But he rekons the ones with just the huge flair like the top ones flow good. Hence my confusion haha.

May sound like a silly question, but ive found the perfect length ones that i want but i can only get them in 45mm. But it says to suit 40mm as well, would 2.5mm of a gap either side be much of a worry??

May sound like a silly question, but ive found the perfect length ones that i want but i can only get them in 45mm. But it says to suit 40mm as well, would 2.5mm of a gap either side be much of a worry??

 

 

It will work but it may hinder your air somewhat. best to get a vaccuum cleaner and a ciggy and do some tests.

 

:P

I remember Fast Fours, back in the days it was actually worth reading, tested this with a flow bench. Yes the full bellmouths flowed the best, but the ones that have the big flare were not that far behind and are a lot easier to make.

 

If you are worried about the 2.5mm gap, grab some of that metal mend stuff and bog it up :P

1. space (limiting factor)

2. type of filter (some filtering recommended)

3. length (rpm range)

4. entry shape (sharp or rounded)

5. material (steel or aluminum)

6. price

 

- plenty of ram tubes/velocity stacks avaliable oem and aftermarket for all sizes.

 

space is the biggest factor by far especially when running filters and it is recommended

to run them, also you need apparently about 1 inch clear space in front of the entry for

flow into the mouth which makes even less space...

 

filters also can be mesh screens or big oiled socks or paper side filters or foam oiled type all

with different sizes and filtering qualities, some are rubbish others great, best ask around and

consider the space factor. i would run fiters even if its just mesh at least ie cut squares of certain filtering

materials, layer them and rubber band them on or buy them ready made all integrated as a unit.

 

length relates to rpm range, as mentioned... longer is more torquey lower rpm and shorter is for

more power high rpm i believe...

 

entry shape has been argued both ways, oem its sharp and aftermarket usually round so i think

theres not much of a noticeable difference, shape is probably more related in ease of manufacturing

but is seems argued that round would have superior flow but I'm not sure. either way its much better

than no velocity stack at all as that just leaves a sharp edge but some people run them like that.

 

material oem is steel and gets surface rust, aftermarket usually stainless or aluminum.

 

price ranges from about $100 to $400 a set of 4, plenty types / sizes avaliable.

May sound like a silly question, but ive found the perfect length ones that i want but i can only get them in 45mm. But it says to suit 40mm as well, would 2.5mm of a gap either side be much of a worry??

 

One word - Daft.

 

Seriously, you might as well not bother with your gap of only 2.5mm.

 

The whole point of trumpets is to create laminar airflow (the opposite of Turbulent flow).

 

As soon as you put a step, be it .5, 1, 2, 2.5mm in your flow path, you will create turbulent flow.

Velocity stacks is just that..... They help to make the power in a certain rev range - long stacks = low rev power / short stacks = high rev power. But you'll only really get the most from them if their matched with the cam/s as well (not a good idea matching a long stack with a cam that makes the power high in the rev range).

 

But it also comes down to how much room you have as well

cory its mick run the short ones will suit car and track and motor better

One word - Daft.

 

Seriously, you might as well not bother with your gap of only 2.5mm.

 

The whole point of trumpets is to create laminar airflow (the opposite of Turbulent flow).

 

As soon as you put a step, be it .5, 1, 2, 2.5mm in your flow path, you will create turbulent flow.

 

 

Couldn't agree more. You'd be far better off with one of the "worse" designs than having a lip inside the port.

Funnily enough, I just looked up from reading this thread and saw my fluid mechanics book, so I thought I'd do some calcs on this......But it started getting lengthy and I've got real work to do.... haha.

although a lip is generally frowned upon in flow when port matching i found

it interesting that a reverse lip can aid flow eg a step down used in exhaust

extractors or the like... so not every lip is bad :jamie: