Single or Individual Throttles (Turbo)?
 

I'm new to the 'blown' world - please help.

We're building a 3.0 Twin Turbo race engine (so must be durable, reliable and simple). I have the luxury of being able to go either single throttle (993 style) or 6x individual throttles.

I assume throttle response (as in n/a cars) will be better? From a racing perspective and considering that revs remain btw 3500-7000 rpm:

Please give me the ups and downs.

Tom

I'm going ITB's. Now consider that there is no off the shelf plumbing and no bolt on IC's. I think it depends on intentions/use. I think it partially depends on boost levels. The 993 intake requires adapters but you probably knew that. I would think if "simple" and "reliable" are in your criteria then why not consider the Carrera intake.

You are thinking EFI, RIGHT??? What type of fuel and ignition controls are you looking into? What compression are you building into it? What type of head mod's and size are you running? Header design?

I think the experts might need more data points to give a good response. Also run this past the guys on Rennlist in the 930 section.

Luke,

Data: Running EFI (Wolf 3D). Currently running 102.6 leaded racing fuel. Ignition is 6x individual twin-coils (crank trigger). Pistons will be 7.5:1 JE racing turbo pistons, cams are 964, heads are ported and flowed (from SC) with twin-spark and ceramic coated. All head ports are matched to inlet and exhaust sizes.

We considered running a set of 993 n/a headers modified to accept the twin turbos. I would like to limit boost to say .8 but it will of course be adjustable.

When I referred to 'simple' and 'reliable' I was just trying to explain that the engine must run at full load for a long time (as opposed to street/drag cars). I do not like fancy tricks, instruments and gimmicks on my cars - I focus on the driving.

I did post on Rennlist too - some good ideas so far.

I guess we're trying to decide wether to spend lots of time and $$$ on a fancy throttle body setup - versus simply keeping it single T/B and crank the boost up .1 bar?

Thanks for the help.

Tom

I would go with dual throttles or single one (depending on turbo packnaging and intercooler design). Whatever miniscule response improvement you gain with ITB's it will dissapear in a sea of turbo lag.

Regarding headers, you don't need equal lengths. Just keep it short and well flowing. With other words, make your own! That way you can have turbochargers where they fit the best.

You can check IF2 engine, it has similar setup and quite high power output:

http://forums.pelicanparts.com/porsche-911-technical-forum/254697-if2-thread.html

Re: Single or Individual Throttles (Turbo)?
 

You are going to like the blown world. I know I do:)

I agree with Goran but if it were me, I would do a single TB. I would also build headers. I would put the turbos close to the lower valve covers. You might have to move the oil tank.

It sounds like a fun project.
Dean

>Whatever miniscule response improvement you gain with ITB's it will dissapear in a sea of turbo lag.

I’ve heard the opposite- that the individual throttle bodies make a disproportionate impact in making a turbo respond faster. Of course I heard this in part from people who make ITBs for turbo motors, but I believed it. If you can swallow the budget I think ITBs are clearly better- the question is are they worth it for you.

Say we consider the ITB's and instead of making a once-off plan as we're busy doing now, we rather just buy a kit...

WHO makes a bolt on Turbo ITB kit?

I know the Jenvey, TWM and similar setups for n/a cars. Are there any kits for Turbo's?

Anyone with experience? We can make the intercooler, the exhaust and the turbo installation, but I do not want to re-invent the deep plate.

Regards, Tom

PS. Goran and his boys must be on 'moonshine' 24/7.

I bought the kit from Souk and Mike. They also showed me some cool "blow through" bonnets they can have fab'd that are simplier and I'm sure less expensive than PMS. PMS has a great setup, but it is spendy.

Jenvey's seemed to be considered superior to TWM's for blow throughs and both are now available with straight shot intakes rather than the older Weber/PMO angled intake runners. They are available in all sorts of sizes to match your ported heads. It is often mentioned as a kit assosiated with Megasquirt but certainly would work well with Wolf. You'd want to use TPS and MAP to control your fuel maps.

I'd strongly consider switching to unleaded race gas for tuning to allow WB O2 and not be restricted to EGT's only. I know some swear you can use O2 sensors for a short term/tuning with leaded but wide bands are kind of expensive for disposables.

Look at PMS for some great pictures of a TT setup with ITB's. Remember to reference the two plenums together because your turbos won't stay symmetrical over time.

Emerald can also set you up with ITB's.

Some guys run 930 CIS fuel pumps alone or in sequence if you wish to stay OEM. I guess dependability is tried but $$ is likely higher for performance than aftermarket.

Headers: have you considered 993TT's if you don't prefer to start from scratch. You'll have to flip flanges on one side. Do a search in some detail from TRE or MB911.

I'm absolutely no expert on this, just about 9 mos ahead in the thought and parts accumulation.

ITB units will make much more power and have better throttle response but are a plumbing headache. If done with a twin turbo set-up you life will be a little less complicated as you can basically split the intakes, ie two intercoolers, two plenums etc.. money no object ITB are the best.

Could you please give me physical explanation of how ITB's "make more power"??

Think about it...if running twin turbo you'll still have twin plenum chambers. Imagine situation with exactly identical plenum design where only difference is that one has three ITB's placed in intake stacks and other has one big throttle body just at plenum entrance.

Where does all that extra power come from?

Frankly, I see ITB's on turbocharged car as collossal solution for non-existing problem. Six TB's are more expensive, heavier, more failure-prone and harder to synchronize than two big TB's. There are also added complexities of getting noise-free MAP signal from six stacks with low volume.

Moonshine?

Goran,

I was in Sweden on holiday a few years back and we went fishing up north in the forests. I met the local postman (tourist guide, etc) who took us down one of the rivers. After a rather large amount of beer (it was a hot day!) he offered me some homemade stuff and challenged me to a few 'rounds'.

Sufficient to say I thought I had gone blind!

He called it moonshine. I thought it was Swedish for arsenic.

Well, it was a great trip to a great place.

Tom

Ahh :) You are talking about "hembränt"!

Yeah, Swedish alcohol laws are quite strict so "moonshining" is popular, especially up north where there isn't much to do but fish and drink booze.

i thought you couldn;t have 2 identical / seperate intakes on a twin turbo set-up because both turbos will never produce exactly the same ammount of boost at exactly the same time ???

You must reference the plenums together with sufficient size tubing.