Blow through turbo, again...

[Guest JAMIE T]

I think I want to go with a blow through set-up like the one Cartech used to offer(pictured in "Maximum Boost"). I have been weighing the pro's and con's of it for a few days now. I really want an old-school looking set-up and have it intercooled. I can easily build the plenum and IC tubing myself. I will be using a stock L28ET long block with a bigger turbo cam. I have a Hayashi Racing triple intake already, I just need some carbs. I think I'm going to use Dellorto 40mm DHLA's. I know I need to fill the float bowls, and I will need a boost sensitive FPR, and a BOV. Anything anyone wants to add?

 

OH! Will I need to take vacuum from all six runners to activate the WG and BOV?

[fl327]

Hey i know what you mean, efi is cool, but there is something so bad ass and old school about a carbed turbo setup, especially with the triples, and a plenum which would let you run a intercooler and a bov, thats just nuts.

 

I think you could just tap the plenum for a vacum reference for the bov and the wga or external, or a vacum line from the compressor side of the turbo to the wga for a signal, but i know that some of the good electronic boost controllers need a a signal from the manifold, air in front of the plenum, and the piping off the compressor side of the turbo, its really nothing since you have tig power.. or you could grab a signal off any ONE of the runners, since if you get off the gas, it would get the signal from any of the runners and not need the signal from all six at the same time since the linkage or cable would open and close all six at the same time anyway..

 

i wish i could tig, it would help me out ALOT. anyways good luck and hope i make sense.

[Guest JAMIE T]

Thanks Len for understanding why I want to do it. I'm not here to argue whether EFI is better or whatever. Also, I can't afford Mikuni's. I can get a set of Dells for cheap. CB Performance has kits and jets for them. I have not ever heard a single bad thing about Dellorto carbs, Lotus used them on there blow-through applications.

 

I wonder if you can still hear that beautiful triple sound when it's capped with a plenum and plumbing?

 

OLD SCHOOL FOREVER!

 

After the '73 is done, I'm building a '65 Bug with 2+liters and blow through turbo set-up. I've already got the bug in unmolested, rust free condition.

 

After that is done, it's gonna be a late '40's-early '50's custom, I want a '54 Chevy.

 

Then, it's on to the bike, by then, I should be about 50. LOL

[fl327]

Im sure you will be able to hear the triples sing, especially when you are forcing boost through them, it should be pretty crazy. may be a little muffled because it doesnt recieve direct air flow like an NA, but im sure it will make a great noise all its own. not enough people take on the carbed turbo setups, since yes the efi swap is getting really popular, but the wangan midnite cars came in three or more different turbo setups, dual su dual turbos, the l28et style setup, and the six throttle turbo intercooled, theres room for it all.

 

next car? if my current plans come through i will be working with jdm engines a lot more, primarily the sr20 but not limited to it, and would need a car to reflect it, plus i really those Japanese turbo motors, im just at a time and place in my life that i want to work with one as a personal car....yet

 

list of prospects

 

Silvia/elcamino looking drift cars with the hatch chopped off and a roll cage in its place, but with a gtr or the sileighty front clip and rear panels, setup for drag racing though....im not a drifter or an autox kind of guy.

 

hicas delete 300zxtt with a rb26dett -finally, a 300zx that could whoop supra @ss.

early 260z with the rb26dett-hey its a 2.6 right? probably wont do it, ive had too many s30s and want to do something new.

 

i would still keep the 280z an turbo L motor car though, hes been true through and through.

 

i really do like the idea of making one of those jspec Silvia trucks you see in the drift videos though, you just dont see stuff like that out here.

[z-ya]

Because you are looking into a blow through setup, make sure your carburetors can handle positive pressure. All sorts of weird things can happen when you start pressurizing the carburetor.

 

Think about this, with a fuel pressure of lets say 9psi, and a manifold pressure of 10psi, what will happen? Will the manifold pressure prevent more fuel from entering the float bowl? Will it prevent the float valve from opening all together? I don't know for sure, but these are the kind of things to think about when planning your project. If you were to lean out at 10psi, the result would not be pretty.

 

If you are using the triples for sure, I would forget about boost, and build a 3.1 with a lot of head work. There are people on HybridZ making over 250HP at the wheels with a similar set up right now.

 

 

Pete

[SleeperZ]

Hey i know what you mean' date=' efi is cool, but there is something so bad ass and old school about a carbed turbo setup, especially with the triples, and a plenum which would let you run a intercooler and a bov, thats just nuts.

 

I think you could just tap the plenum for a vacum reference for the bov and the wga or external, or a vacum line from the compressor side of the turbo to the wga for a signal, but i know that some of the good electronic boost controllers need a a signal from the manifold, air in front of the plenum, and the piping off the compressor side of the turbo, its really nothing since you have tig power.. or you could grab a signal off any ONE of the runners, since if you get off the gas, it would get the signal from any of the runners and not need the signal from all six at the same time since the linkage or cable would open and close all six at the same time anyway..

 

i wish i could tig, it would help me out ALOT. anyways good luck and hope i make sense.[/quote']

 

You cannot tap the plenum, as there will be no vacuum there; it's in front of the throttle butterflies. You can get a signal off a single runner, but I hear you may want to connect several togther and make a combined, even source, as the pulsing may not make a reliable signal that can activate a bypass (BOV) valve, or operate a brake boster.

[Guest JAMIE T]

If you are using the triples for sure, I would forget about boost

 

Forget about boost? You gotta be kidding!

 

 

 

I hear you may want to connect several togther and make a combined, even source, as the pulsing may not make a reliable signal that can activate a bypass (BOV) valve, or operate a brake boster.

 

That's what I was thinking.

 

 

make sure your carburetors can handle positive pressure

 

Side draft Dellorto's have been used by Lotus for factory equiped blow-through turbo Esprit's. When above atmo is pushed through a Dell, I think all you need to do is fill the float with foam(or get solid floats) so it won't crush under boost. I don't think any of the availabe side drafts require the entire carb to be in a pressurized box.

 

What is the maximum boost anyone has heard of being used with blow-through side drafts?

[TimZ]

make sure your carburetors can handle positive pressure

 

Side draft Dellorto's have been used by Lotus for factory equiped blow-through turbo Esprit's. When above atmo is pushed through a Dell, I think all you need to do is fill the float with foam(or get solid floats) so it won't crush under boost. I don't think any of the availabe side drafts require the entire carb to be in a pressurized box.

 

What is the maximum boost anyone has heard of being used with blow-through side drafts?

 

You need to make sure that the float bowls are pressurized to the same pressure as the plenum, or no fuel will flow. Obviously, the fuel pressure needs to be regulated to ~4psi above that (or whatever pressure the Dellortos generally need). The Mikunis have a third port on the front of the carb, which is a pressure reference port for the float bowl. This is why they never required a pressurized box. This port needs to see the same air pressure as the carb throats. Presumably the Dellortos have a similar feature.

 

I used to run the Cartech setup up to about 15psi. You might be able to go a bit higher. If you do, I'd go with forged pistons - it's quite a bit harder to tune this setup, and harder to tell what's going on before it's too late.

[dalesince59]

i'm doing a similar setup on a small block z with four 40mm dels. i got my carbs direct from italy from a guy who sells them on ebay.Cheap! ,matched and nice. carb mods for the blow thru are as follows. foam or filled brass floats. sealed or o-ringed throttle shafts. a static fuel pressure of four to five lbs. plus one lb. of fuel pressure per lb.of boost pressure, this is where the boost referenced fuel reg. comes into play. if for example you are putting out 15 lbs. boost you will need 19 to 20 lbs. of fuel for engine supply and to overcome the 15 lbs. pressure that is in the float bowl. in a blow thru set up, if the float bowl is not pressurized as well, the fuel will not be able to enter the fuel stream.

good luck

[Guest POKINATCHA]

Its cool to see some other guys still interested in using carbs. I'm actually in the (slow) process of mounting a turbo rotary in my Z, and I'm using a 48mm Dellorto in a blowthru setup. I think CB performance sells turbo prep stuff for the Dell's.

[Guest JAMIE T]

WOO HOOO! Finally some folks NOT trying to talk me out of it.

 

Tim. So, would Solex carbs(presumably the same as a Mikuni) be better than the Dells? The same guy who has the Dells, also has a set of 40mm Solex carbs. How did you like the Cartech set-up? I wish I could find larger carbs for a better price. The 40mm Solex carbs are very reasonably priced. Thanks guys for the tips.

 

 

Pokinatcha, CB Performance told me a few days ago that they couldn't get parts anymore and gave me number to a place called ACE. I called Fri, but the guy was out of the shop.

[Guest POKINATCHA]

Well, shows what I know. ACE, huh? Never heard of them. Let us know how it turns out.

[TimZ]

Tim. So, would Solex carbs(presumably the same as a Mikuni) be better than the Dells? The same guy who has the Dells, also has a set of 40mm Solex carbs. How did you like the Cartech set-up? I wish I could find larger carbs for a better price. The 40mm Solex carbs are very reasonably priced. Thanks guys for the tips.

 

Sorry, but I don't know much about the Dellortos, so I can't help you with which one is better. Do you have a link to a picture of one?

 

The cartech setup is intended for the Mikuni 44phh carbs, and as I recall, these aren't the same as even the Mikuni 40mm carbs as far as the mating surface for the plenum, assuming you want to use the cartech plenum.

 

How did I like the setup? Well, it did quite well at WOT, once I got a clue as to how to set them up - remember this was about ten years ago and there wasn't an internet support group out there, so I was pretty much on my own.

 

The main problem that I had was with driveability issues - they really didn't like fast throttle transitions - dropping from fifth to third and nailing it almost always resulted in falling flat on your face for about a full second or more. Really annoying. I think part of the problem was with the plenum being a bit too small, and when you would open the throttles in an off boost situation, they would create a weird pressure fluctuation in the plenum which really messed up the flow through the venturis.

 

BTW, you really couldn't hear the Mikunis at all any more once the plenum was in place.

[Guest JAMIE T]

Well lets see. I bit the bullet and bought those Solex carbs off ebay. After emailing a friend who specializes in Mikuni's, he informed me that the ones I had already bought are the german type Solexes. The seller says they are italian made Solexes. Either way, they ARE NOT MIKUNI's. So, that sucks. My friend who is the Mikuni Guru is gonna get me a price on some 44phh Mikuni's. I hope he's got some lube . I guess I bought myself some expensive paper weights. I'll probably still use them on something sometime.

 

Thanks for all the advise. One set of Mikuni 44phh's on ebay for $300 right now, but they still have like 8 days left on the auction. I expect them to get to $800 or more including the manifold(which I already have.)

 

Tim, what type of fuel pump were you using with the Cartech set-up? Which regulator did you use also?

[TimZ]

Tim, what type of fuel pump were you using with the Cartech set-up? Which regulator did you use also?

 

I used the stock EFI pump, regulated by a pressure referenced Solex regulator that came with the Cartech setup. It regulated the fuel pressure to 4 or 5 psi above the plenum pressure. Because of the low pressures required, that pump was adequate for the application.

[ZROSSA]

There is a fellow on the blow thro turbo group at the moment that is talking about using the su's. Austin rover made a car in the 80's called the maestro (or similar) that was a 1.8 lt blow through turbo trough a single su. They could get 200 hp out of this set up. The su had to be sealed and they ran a high pressure fuel pump like a fuel injection unit and a pressure regulater that kept the fuel pressure about 4 psi over the boost pressure. I am just going from what i remember reading. Aparently they have all the details in the blowtrou groups archives so have a look.

 

Cheers

 

Douglas

[Guest JAMIE T]

ZROSSA, I am a member of the Yahoo Blow-thru Turbo group. I just joined a few days ago. I'v gotten a few answers from over there, but mostly got the good info from here. I'm NOT going to use SU's. Honestly, I am mostly doing this for the looks, and nostalgia. My car has that old school Wnagon Midnight flavor. So, the triples are my bag.

[madmatt48]

I will also be utilizing the blow through carburating setup on my 1979 280zx L28 super/turbo project as soon as my parts arrive. I am going the Demon 650cfm blow through route with a clifford 4-barrel intake manifold. I will utilize a 2 inch carb spacer with a 3 inch tall carb hat with two 2 inch inlets. One for the TO4e turbine discharge, one for the paxton novi 1000 supercharger.

 

I am currently running 280zx turbo factory injection with RB26DETT 440cc low impedence injectors with a n/a air flow meter which I installed on the turbine discharge side just prior to the manifold inlet(this allows for the flapper style air flow meter to open upon boost instead of opening depending on air intake demand). Also have a bosch boost sensing fuel pressure regulator to up the fuel pressure upon every pound of boost. That way my turbine intake is clear for the custom cold air intake. ARP head bolts are used to hold the P90 head on with the 1.5 mm steel head gasket direct from Japan. Not fond of the stock fuel injection manifold, looking forward to the 4-barrel blow through Demon set-up. More to follow when I get it all on-line...

[S30TRBO]

and I thought Jamie T was back it's a 5 year old thread.

 

Seriously, good luck on the blow through madmatt. Post a new thread with some pics and a write-up..

[savageskaterkid]

I will utilize a 2 inch carb spacer with a 3 inch tall carb hat with two 2 inch inlets. One for the TO4e turbine discharge, one for the paxton novi 1000 supercharger.

 

 

I don't mean to go against this, but how well will this actually work? The reason I say this is, the supercharger would be making boost at low RPM's and be pushing through the piping, and actually surge the turbo wouldn't it? You'd need some kind of way to regulate it where it wouldn't actually lag the turbo.