turbo piping size

[brian89gp]

What I have now:
2" outlet on turbo into 45* bend, to 90* bend, to 90* bend, to 2.25" IC.
2.25" IC to 2" pipe to 90* bend, to 90* bend, to 45*, to 45* to 3" TB.

http://www.brian89gp.com/images/turbo/intake/DSCF0034.JPG

http://www.brian89gp.com/images/turbo/intake/DSCF0004.JPG

What I notice is that I have quite a bit of throttle lag (not turbo lag). I can snap the throttle and its just real sluggish to respond which I know is due to the 2" press bent tubing. I am re-doing it all which is what I need help with. I'm keeping the Saab 900 IC cause it seems to be doing a decent job, after some spirited driving in 30* weather I open the hood and feel the plenum and its cold

So for the piping, what would be best? 2" - 2.25" right out of the turbo to all 2.25" piping to the TB. Or should I go with 2.25" to the IC and use 2.5" or 3" from the IC to the plenum to increase the volume of air before the TB?

[RacerX11]

Did you give up on the air-to-water IC idea?

Is there any way to physically mount the IC in the fenderwell, with a scoop to direct air to it, much like a fenderwell CAI? You will lose some efficiency with the decreased airflow, but the increased throttle response might be a good tradeoff. Other than using mandrel bends to help flow, and keeping pipe volume to a minimum (2" or 2-1/4") to reduce lag, it is going to be tough with your existing pipe routing path.

If it was my car, I would run 2-1/4" all the way from the turbo to the IC, then 2-1/2" from the IC to the TB.

BTW, you can get the mandrel-bent elbows cheap from JC Whitney.

Marty

[brian89gp]

The water-air idea was actually just a way to shorten the piping length, after looking at the costs though I'm going to stick with air/air till for some reason i need water/air.

I'll have to test fit it in the fenderwell to see. Only problem is that I would have to redirect a portion of the radiator air over there. How much air do you think I need? I could probably attach some 2.5-3" plastic dryer ducting to one of the bumber openings and route it to a plexiglass box that the IC sits in.

Would welding 2 IC's together so that it is twice as thick (one behind the other) be benificial?

For the IC to plenum, is it still wise to keep a small diameter pipe here? I notice that with 2" piping that 60% throttle and up feels about the same, its real different driving it. How much would having a 3" pipe here hurt turbo lag etc (keep in mind that all but 1st gear i can be in boost at almost any RPM)

[93LuminaZ34va]

I've always heard its best to keep the same diameter intake duct work as the outlet on the turbo... so if your boost side of your turbo outlet is 2.0 inch inner diameter, then your intake tubing should be 2.0. Beyond that, I don't know too much about how to run the tubing..... just figured I'd drop in my $.02. The difference in the size of your throttlebody may also throw it off, I remember seeing something about that too, because as the air flow goes from the 2 inch piping to the 3 inch opening, there is a loss in pressure and air flow velocity....

[Fierofiend]

Hmm.. I running mine 2.25 to the intercooler, then the size of the TB from the intercooler.

[93LuminaZ34va]

I'm not saying it won't work, its just ideal to have the same sizes from turbo to throttle body........

[Norm '88 GT]

brian89gp, your piping looks great. You are correct that it might be too small. I went from 2" to 2.5" from the Powerdyne SC to the Izusu NPR IC. I still have 2" from IC to TB and think it might not be beneficial to increase it as there is a pressure drop after the IC. The article below is from autospeed.com which gave me inspiration to increase the diameter and increase the 3" radius 90 bends to 5" raidus bends. One of these days I'll post pics of the engine bay.

~~~~~~~~~~~~

With the use of remote filter airboxes (and intercoolers in all turbo cars), there's plenty of plumbing through which air has to flow before it can become part of the combustion process. Then of course after the burn has happened, the exhaust - again, a long piece of bent pipe - has to be negotiated. The flow through these bends therefore becomes an important part of performance. Sometimes in automotive modification we tend to think that we are inventing something new, but there are plenty of other industries where the flow performance of long pieces of bent tube is critical to the performance outcome.

I recently picked up a book first published in 1960 - the Handbook of Air Conditioning System Design, written by engineers of the Carrier Air Conditioning Company. It's an extremely comprehensive manual of refrigerative air conditioning design, but in addition it has extensive chapters on facilitating the movement of air through pipes - the latter a fundamental of air-conditioning systems. The pressure drop experienced is even more critical in these applications, where pipe runs are much longer than you'll find in any engine bay, and the pressures being dealt with are so much less. So these guys looked long and hard at the restrictions posed by bends, elbows, 180-degree hairpins - and quantified the results.

So let's cut to the chase - what are some of the useful figures? Let's take a 3-inch tube: that's pretty common these days on both high performance exhausts and intakes. A tight 90-degree bend (where 'tight' means a radius about equal to the diameter, ie in this case 3 inches) poses the same restriction as 7.5 feet (2.3 metres) of straight pipe!

A long radius 90-degree bend (a bend radius of 4.5 inches, or 11.4cm) has a flow restriction equal to about 5 feet (about 1.5 metres) of straight pipe.

A 45-degree bend? Well, one with a radius of bend the same as its 3-inch diameter has an equivalent flow restriction of 4 feet, or about 1.2 metres. A 180-degree bend with a 1:1 radius/diameter? It's got the same flow restriction as 12 feet of straight pipe - that's an incredible 3.7 metres!

Get the picture? Those bends - even when they are relatively open - drop flow to a major degree. If the mass of air contained within the pipework isn't critical (eg as it is for intercooler plumbing, where throttle response loss needs to be minimised) it makes a helluva lot of sense to go much longer rather than put in tight bends.

And we've all seen those intercooler plumbing constructions where someone hasn't bothered using a bend at all - instead they've welded a 90-degree mitred join into the plumbing. The Carrier book suggests that in 3-inch tube, such a join has the equivalent flow restriction of nearly 4.6 metres of straight plumbing....

And what about other pipe diameters? Some other data from the book is reproduced here:

Losses in equivalent feet of straight pipe:

SMOOTH BEND ELBOWS
Pipe Size 90-degree standard 90-degree long radius 45-degree standard 180-degree standard
2 inch 5.0 3.3 2.6 8.2
2½ 6.0 4.1 3.2 10
3 7.5 5.0 4.0 12
3½ 9.0 5.9 4.7 15
4 10 6.7 5.2 17
5 13 8.2 6.5 21

'Standard' = radius/diameter ratio of 1. 'Long Radius' = radius/diameter ratio of 1.5.

MITRED ELBOWS
Pipe Size 90-degree 60-degree 45-degree 30-degree
2 inch 10 4.5 2.3 1.3
2½ 12 5.2 2.8 1.7
3 15 6.4 3.2 2.0
3½ 18 7.3 4.0 2.4
4 21 8.5 4.5 2.7
5 25 11 6.0 3.2

Quite a while ago - in fact in June 2001 - I mentioned how the clothes prewash cleaner Preen worked very well at getting brake dust off alloy wheels. At 81.5 per cent liquid hydrocarbons, it is very effective and much cheaper than most alloy wheel cleaners. However, what I didn't tell you at the time is that right when you're cleaning your wheels it's also possible to get a very good feel for the camber settings you're running on your rubber.

Huh?

It works like this. Step 1 is to clean your tyres and wheels while the car is standing on light-coloured concrete. Spray the Preen on...

...then wash it off rapidly without using too much water. You just want enough to get off the chemical and the brake dust, not flood the place.

The water and its accompanying dirt will form a puddle around the base of the tyre.

Give it time to dry and then when you move the car away, hey presto! you'll see this..

...or maybe this.

Have a look at the two tyre footprints and you'll soon see that they show a different shape. This was one of the front tyres, where I had the car set up with a little more negative camber (ie the tyre leaning in at the top) than for the back wheels. You can clearly see how the inside of the tyre is being pushed harder against the pavement than the outside - in non-cornering situations the inside of the tyre is taking a greater part of the load.

One of the rear tyre footprints shows that there's still negative camber being used, but less than that the front.

Now I am not going to suggest that these dirt footprints are going to put an electronic wheel alignment machine to shame, but they can be startlingly clear in showing the change in the shape of tyre contact patch caused by camber variations. Plus when you can do it for nothing at the same time as you're cleaning your wheels, then...

Another popular 'tips' type of story that we ran a while ago was "Ballistic Bellmouths" in January 2002 (if you don't know what advantage a bellmouth provides - read the article). The story covered how to produce a bellmouth from the stainless steel eggcups available then (as they still are) from Woolworths stores in Australia. The resulting bellmouth had an opening of about 60mm with a taper down into the tube.

But what if you want different-sized bellmouths?

I've been keeping my eyes open since and have found an excellent source. They are cookware tins and plastic trays designed to produce jellies and cakes which look a bit like large donuts - the finished foodstuff will have a big hole in the middle. The jelly containers (maybe microwave cakes as well?) are plastic, while the oven-cook cake tins are available in either coated steel or aluminium constructions.

When they're turned over, the bellmouth formed through the middle can be clearly seen.

Then it's just a case of using some hand tools (sharp knife, file, sandpaper) to remove all the surplus plastic around the bit that's wanted. This particular bellmouth is about 90mm in diameter across the outer edge and tapers down to a 52mm tube size. On a small car it would make an ideal engine intake bellmouth or brake duct bellmouth.

If you want bigger, this monster should suffice. It's a cake tin and the central hole (when that little flange has been filed away) is a whopping 100mm (~4 inches)! Depending on where you trim the edge of the bellmouth, the overall diameter will be about 180mm. As an engine airbox intake or brake duct this is a bloody good thing - all for a new price of about ten Australian bucks from your local cookware supplier...

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[brian89gp]

I'm not really all that worried about flow or pressure drop. This 60%+ on the throttle feeling the same is really annoying me and I want to get rid of it at all costs, having a snappy throttle response again wouldn't be too bad either.

I'm thinking of putting the IC in the fenderwell, have to do some measuring this weekend.

[Streetrodder83]

Welding 2 IC together would net some gains, but not as much as increasing core frontal area would. The last half of the intercooler is only doing about a 1/4 of the cooling task. How are you maintaining the proper A/F Ratio. Depending on what you have you may be bogging under an overly rich condition. I don't see the piping as the issue, ran some math on just a 2 in system and you shouldn't be exceeding its capacity.

[brian89gp]

Its not a/f related bog, i'm sure of that. True the 2" piping is still adequate for the flow requirements, but it also has real horrible throttle response. For the most part I can blip the throttle and the engine just gives a grunt, if i blip the throttle and hold it for a second then the engine will respond. Also, as I said, the 2" pipe directly into a 3" TB provides for very interesting side effects, the guy (sorry, forgot your name) with a turbo hybrid in a Jimmy was talking about the same effects except to a lesser extent. Mainly half throttle and full throttle pull and feel exactly the same except WOT makes more noise.

[RedZMonte]

Larger all around the better to a point. i would run at minimum 2.25" mandrell bent. or 2.5" press bent. tims has 2.25" mandrel bent and it seems to be fine. I am also going to be running 2.25" mandrel.... possibly 2.5" mandrel. my intercooler is 2.5" in/out.... so i most likely will run 2.5" up to the throttle body then flare the pipe up to 3" where it meets the coupler on the throttle body. i haven't decided if i want to boost accross the front of the motor or in and out the drivers side fenderwell.

RedZ

[Norm '88 GT]

I just upgraded tubing from the IC to the TB. I was running 2" with one tight 3" radius that I knew was some restriction at higher flow. I have been doing datalogs in the warmer weather and my A/F ratios held from the winter.

I am running 2.5" from a Powerdyne blower, which has an outlet of 2.75", to a IC opening of 2.5". From the IC to the TB I upgraded today to 2.25". Quick datalog show that my WB O2 sensor was having to add fuel from 3K on up. I did one 3rd gear pull and my 36# injectors were at 80% DC and 10 psi at 5100. You do the math. I changed the fueling and will do more datalogging in the next few weeks.

[Norm '88 GT]