External wastegate vrs. wastegated housing.

[RonA]

Does a good external wastegate flow much more air around the top turbo than a wastegated housing?

Ron

 

[Hohn]

Ron, a good external WG will flow WAY WAY more than almost any WG housing, unless that housing is so huge that it defeats the need for a WG in the first place.



An external will flow more, but it does bleed iff more of the energy that feeds the turbo (heat and pressure). Sometimes this is good (small housing, way overfueled, screaming drive pressures). Sometimes this is bad, because it means less overall thermal efficiency.



In a twins setup, and External can be used to expand the envelope of "matched" turbos performance. IOW, a perfectly "matched" compound setup makes you choose between spoolup and top end flow (just like a single does, only the stakes are higher). An external gate lets you get a little more spool and keep the top end.



Keep in mind, that an internally gated housing is a choke point. The overall flow of an internally gated housing is STILL determined by the overall size of that housing, to a certain extent.



An external gate has a MUCH higher flow capacity, and therefore can do a better job of preventing overspeeding in the top charger in a compound setup.



Justin

 

[HoleshotHolset]

Yes. Without a doubt.



Most internal wastegate 'flappers' are pretty small and very inefficient in design. Their only advantage is keeping the package nice and compact... and if you already have a wastegated housing... having a twin-turbo setup with one is cheaper than buying an external WG.



Matt

 

[RonA]

What would be a good brand and size to get for the towing twins I have?

Ron

 

[Hohn]

Tial is the best brand, IMHO.



38mm should be plenty big.

 

[justinp20012500]

Yes. Without a doubt.

Most internal wastegate 'flappers' are pretty small and very inefficient in design. Their only advantage is keeping the package nice and compact... and if you already have a wastegated housing... having a twin-turbo setup with one is cheaper than buying an external WG.

Matt

Half to agree with Matt and give some clarification...

The flapper in my waste gated 14 housing was removed in favor of a bigger one, I also opened up the hole to accomadate the bigger flapper. (As big as the housing allowed) I also milled a potion of my 1/2 backing plate to allow the "flapper" (for lack of a better term) to open farther. I conjunction of the milling the plate and the bigger flapper I also plasma cut the divider back to allow all six cyclinders to be equal in pressure.

The waste gate on the HX opens up @ 20 PSI and starts to dump exhaust into the big turbo.

I am in the process of plumbing my 0-35 psi gauge to monitor what pressures the cold pipe is seeing.

 

[Jim Fulmer]

Internal wastegates work very well if they are setup correctly, why do you think the PDR setup works so well... . case in point my B/B make just shy of 40 psi by it's self now with that setup, on the 3B's it's in the lower 30's. The externals work good also but can be more of a pain with leaks ect. If I were building a setup for myself and my own design it would be with an external gate.



Jim

 

[Nick2]

Something's been bugging me for a while, is it possible to use an external wastegate and one BIG charger. Lets say for instance an HT3B with the smallest little housing you could find to spool quick and a wastegate so top end doesnt get traded off?? Does the big charger need a big turbine housing to get it spinning or something? - what am I missing?

 

[drawson]

My PDR set up Twins works extreemly well. I am seeing 38 PSI out of the HB3T and the waste gate is wide open at 24 PSI on the HX-40. This set up spools faster than the PDR HX-50/15 did and has alot more top end. Piers know who to make the internal waste gate work well!!!

 

[Idaho CTD]

Nick,



You can use a external wastegate with a single and it will keep your drive pressures from going too high on the top end. It will also control the boost to keep the turbo in it's efficiency range. Another thing it will allow you to do is run a extremely tight exhaust housing without high egt's, drive pressure, and boost. Basically it will allow you to tune for the most power.



Nathan

 

[Nick2]

thanks nathan,



it sounds like the big single with ext wastegate would be a decent idea for the guy short on funds, with a manual trans and little towing to do... . here I go talking again

 

[Hohn]

If you're in those shoes, just contact Uncle Joe. His charger is a lag hog, but enough for him to tow his shoebox trailer and still dyno 799hp with a single.



ustin

 

[HoleshotHolset]

is it possible to use an external wastegate and one BIG charger.

Sure... why not.



BUT, keep in mind that big honkin turbos have heavier (and harder to spin) rotating assemblies. A small housing will help with this, but it's still going to be a lag pig.



A combination of: lightweight compressor/turbine wheels, shaft, ball bearings, and VGT/VNT would be mighty tempting. Without all or at least some of those things... it's going to be a lag pig.



These factors (and others) affect lag: Engine RPM, engine load, temperature delta across the pinwheel, pressure delta across the pinwheel, rotating assembly mass, agressiveness/trim (is that a word?) of the pinwheel/compressor wheel, etc.



Matt

 

[NPloysa]

Matt, if I were to run an HT3B with only my FMS box, with the smallest exhaust housing I could find, how do you think lag would compare to my stock 35 (I'm at 6000 feet)? Obviously it will lag more, which is a trade off for higher HP and lowering EGTs. Later I could add Mach 2s and put a slightly bigger exhaust housing on it, if needed. What boost numbers do the HT3Bs perform at max? And what pressure should I wastegate it at?

 

[Idaho CTD]

A HT3B as a single is WAY to big to tow with at 6000'. There are smaller housings then the common 22/23cm housings but I doubt they would be small enough to run at sea level without a ton of smoke. Like Matt said the rotating assembly is just too big to overcome even with a tight housing. Heck a full B1 is probably too big to tow at 6000' with a 24v.

 

[NPloysa]

Idaho, I will be running empty! Yes, altitude is a killer. DHatfield, who lives here in the Springs also, has an HO with an Edge Comp, Super Mentals and a B1. Does good on only injectors, but with 5x5 on the box, may as well be a coal train!

 

[HoleshotHolset]

Even running empty... the air's just too thin up there to run a big single... UNLESS you run a VGT/VNT with a ball bearing center section.



I can't see anyone running anything much bigger than a B1 for a single... after that... it's a lag pig and the end result doesn't justify all the BS you had to go through to bolt it on.



There are some 'street driven' pulling trucks out there running pretty big singles... but they smoke like a tire fire out in the flatlands of Indiana - so you can imagine what it would be like at altitude.



Matt

 

[NPloysa]

thanks guys!



edit: stupid me! first of all, i want to say sorry as i am not trying to hijack the post!



second of all, i was asking about the htb2, not the ht3b! i asked about the htb2 thinking we were all talking about it and not the 3b. sorry, you guys are totally correct about the 3b being way too big! maybe a 2b would do though.



nick

 

[SRadke]

HTB2's would work great at 6000 ft for a towing single. I have a Killer B2 with the 14 cm^2 housing and it spools nearly as fast as my stock HY-9.



-Scott

 

[NPloysa]

I'm not going to tow, though. Should I go bigger since I will be running empty?