Opel GT Forum banner

1 - 20 of 110 Posts

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #1 ·
I've had this recurring idea of a 1.9 turbo motor with some of the flaws of the past one fixed. I'd been thinking of keeping it quiet until I just said here it is but I have too many questions I don't know the answers to for that.

The first concept is the exhaust and I've tried to put it on paper with little to no success so I'll describe it. Using a blank flange from Bob (thanks for doing them ) on the 1 and 4 ports use a weldable fitting 45 to point both down and towards the center of the motor. From there a short piece of tube and another 45 to roll it straight towards the center of the motor. Another piece of tubing and then 90 it straight up so the two are joined up. For the center two use a 90 off the flange and make a loop going down to put all 4 in a 2x2 configuration pointing up and joined together. Top this off with a plate cut to fit a turbo exhaust inlet flange. The flange would be roughly 4 inches out from the head and be in the exact center and at about bottom of the head ports for height. This is all to keep the lag to an absolute minimum and not have plumbing that requires the removal of other things to get too. It would all stay above the motor mounts and come out in 1 piece.

I have been looking at the injection but to me that's a new can of worms I've never done before. Placement of the turbo looks like it will suit whichever way I go as far as a suck or blow system. so I need to look at this more carefully before I start welding or buying more parts.

I did some looking today and found a Volvo turbocharger from a 86 740 for 150 bucks that has the wastegate on it already. weldable fitting my cost are about 4.25 each so that is looking good and they have good stock too.

questions so far are the flange for the turbo inlet on the exhaust side 3/8 ok or need to go 1/2?

How critical are the lengths of the runners for the exhaust and are they measured at center line to give equal lengths?

Any comments on the Volvo turbo?

Can I make an injection intake for the motor?

Sorry very long winded but I've been holding it in.
 

·
Super Moderator
Joined
·
13,844 Posts
questions so far are the flange for the turbo inlet on the exhaust side 3/8 ok or need to go 1/2?

3/8 should be fine. I made the flange for my friend's 270 hp turbo rallycar from 3/8" material last year, he's raced it all year long with no problems at all (other than breaking halfshafts and cv's)

How critical are the lengths of the runners for the exhaust and are they measured at center line to give equal lengths?

For a turbo it's not that important. The turbo relies mostly on the energy from the expanding exhaust gasses rather than exhaust pulse energy to drive the turbine.

Any comments on the Volvo turbo?

Probably a T3 with a .48 exhaust A/R, right? Pretty common, cheap to rebuild and service (about $100 for an overhaul kit), and reliable as long as it has clean oil. Probably will cap at around 220 hp or so. After 17 psi of boost it runs out of its' efficiency range in a hurry, so an intercooler would be mandatory if you want to approach this boost level.

Can I make an injection intake for the motor?

Sure, I don't see why not? Could probably free up a bit more room under the hood. Shorter runners would help with the turbo lag as well.

BTW, do you want me to make a set of those short 'square-to-round' adapters to merge the flange to a round tube like I did on the turbo Manta?
http://www.opelgt.com/forums/showpost.php?p=25659&postcount=44

Bob
 

·
Registered
Joined
·
6,344 Posts
Well, Rally Bob answered all the questions, with his usual expertise and experience, so I'll add just a comment or two. Lotsa years ago an article was done about using a turbo on a GT, the bottom line was, box stock motor with 8 lbs of boost, the horse power doubled, to a reported 160-180 HP. What year or pistons I don't know. Fuel injection, all I can say is what I know about my 3.4 SFI, there are a lot if inputs from the engine to control injection pulses as to when and how long. What the aftermarket systems require, I have no idea, I'll let the other folks delve into that area. Is a bolt on system feasible? It sounds good and may have a market, depending on total cost. Maybe you two should do some networking. :D
 

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #4 ·
To make it quick and easy as I was planning to go straight off the flange to the 90s or 45s I was planning a jig and would probably do the press for it. I'm so glad you posted ...thanks.
 

·
Member
Joined
·
240 Posts

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #6 ·
Bob thanks for reminding me to look at that pic. Those flanges are an Id fit not an OD one. Give me a price on an initial 6 of the square to rounds. How thick is the tube you use? how short can those be made up? Will they fit inside a 1.5 weld 90 or a butt weld type? spacing is everything so I'd like to have an idea of od diameter to work off. Wow not off the drawing pad and seeing problems. looks like another oportunity to accell.

I'll try to keep it on target but it's hard to do on this subject. From a design concept I've seen easier ones.

If the lengths of the runners aren't that important can I choke up closer to the motor and a bit higher so I can go under the turbo for the intake?
 

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #7 ·
Ok let me throw another idea out there. So far I would have a tubo mounted and plumbed high and tight next to the motor about where a stock carb would be but maybe a bit closer to the head.

Cut off the flanges from a stock intake and weld on about a 4 inch runner set with injector bungs pointing toward the intake valves. From there weld on a 3 inch throttle body necked down to 2 inch at the throttle valve. Run both turbo outlet and throttle body inlet through the front radiator passenger side area to an intercooler mounted in front of the radiator on the passenger side.

So far this idea if usable would keep it all closer to the motor than a set of twins. It would also keep it out of the heater box area completely.

A note on a few things I found while digging.

1 Depending on injector costs the Megasquirt might be cheaper than a sidedraft to fuel it.

2 I'd need a second water temp, an oxygen sensor and throttle positioning sensor to make it work.

3 I have no idea yet for the air intake.

4 I think it should go on a fresh late model bone stock motor to keep it simple.
 

·
Super Moderator
Joined
·
13,844 Posts
nobody said:
How thick is the tube you use? how short can those be made up? Will they fit inside a 1.5 weld 90 or a butt weld type?

If the lengths of the runners aren't that important can I choke up closer to the motor and a bit higher so I can go under the turbo for the intake?
The ones I made for the turbo Manta were .095" thick steel, and they were 1.5" x 1.25" square at the header flange, but ended up being about 1.675" OD at the round end where they butted into a 1.25 pipe weld-el (same OD plus-or-minus .020"). I think I made them about 1.5" long, but they could be shortened up another 1/4" at least. Not much more, because then you get into an interference issue with the intake flange bolts (wrench/socket fitment).
Keep in mind 3/8" of that length goes into the flange itself....

Yes, it may be possible to put the turbo up high and the intake down low, I was thinking this very same thing. For EFI, the runners are all 'dry', that is, there's no fuel in them except where the injectors are. So it doesn't matter really if the air flow 'up' or 'down'. I'm going to try to make a mock-up of this in the next few days and will post some pics here. Hopefully it will give some ideas....

Bob
 

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #9 ·
Thinking about it more and after doing some more reading and hunting the easier way to do the short intake would be to modify an existing throttle body to fit the Opel intake flanges. Any ideas of one that might be a good donor?
 

·
Super Moderator
Joined
·
5,924 Posts
nobody said:
Thinking about it more and after doing some more reading and hunting the easier way to do the short intake would be to modify an existing throttle body to fit the Opel intake flanges. Any ideas of one that might be a good donor?
Do you mean the stock intake, or the '75 Bosch L-Jet intake, or some other throttle body that you would modify to fit up to the intake ports on the head? If you are looking for a throttle body to fit the stock intake, this might work. It is a VW sourced EFI that is on a GT for sale in here Calgary. It seemed to bolt right up to the Solex/Weber pattern. The owner didn't know what kind of VW it was from, but I would guess mid-80's Rabbit/Jetta. HTH
 

Attachments

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #11 ·
Boy that is almost spooky it even has the throttle cable mounts like for a manta or wagon. I'll hunt that one down if at all possible. That would drop the price considerably to have something like that.
 

·
Member
Joined
·
240 Posts
kwilford said:
Do you mean the stock intake, or the '75 Bosch L-Jet intake, or some other throttle body that you would modify to fit up to the intake ports on the head? If you are looking for a throttle body to fit the stock intake, this might work. It is a VW sourced EFI that is on a GT for sale in here Calgary. It seemed to bolt right up to the Solex/Weber pattern. The owner didn't know what kind of VW it was from, but I would guess mid-80's Rabbit/Jetta. HTH
That looks like one of those mechanical FI sytems with injector bungs welded to a stock intake.
 

·
Super Moderator
Joined
·
5,924 Posts
garrymc said:
That looks like one of those mechanical FI systems with injector bungs welded to a stock intake.
Quite right, I called it an "EFI", but it is actually an "FI". The mechanical injector sits in the nose of the GT. And the injectors were indeed threaded into bungs that were skillfully welded into the stock intake. But the interesting part is how the throttle body bolts right on to the carb pattern on the factory intake. Do you know what model and year they came on?
 

·
boomerang opeler
Joined
·
5,636 Posts
have you considerd single point EFI (looks like a carb but has an injector inside) it would be a straght swop or just an addapter plate depending which one you got :)
i think it would be ok as a blow through with better seals on the throttle plate
will post a pic if you need to see what it look like :D
 

·
Super Moderator
Joined
·
9,751 Posts
Baz;
What you're describing sounds like that T.P.I. (tuned port injection) that GM used a few years back. Or the T.B.I. (throttle body injection)
 

·
boomerang opeler
Joined
·
5,636 Posts
that may well be what its called over there:)
i think it would work well with good seals as the harness can be removed from the main harness very quickly and only needs a few sensors fitted to the block ( temp, crank maybe relocate the air temp )
 

·
Super Moderator
Joined
·
13,844 Posts
Only problem with TBI is the injectors are mounted up near the plenum, so the intake would remain a wet-flow intake (air and fuel travel through runners). So distribution is limited by the intake's inherent design. Iffy at best with a turbo, where a correct air/fuel ratio can make or break the engine.
 

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #18 ·
Ok for my next batch of stupid questions. I picked up a multiport EFI manifold for 30 bucks today. I picked a GM model so I could keep it cheap and it has the longest straight section before it mounts to a motor that I found. It also has the cold start valves, injectors, fuel rail, and wiring loom with the mating plug.

1 Do I cut the flanges off a 1.9 intake to use with the runners on this or do I cut the bungs and mounts and use more of the stock intake?

2 How in the wide world of sports would you fit a cold start valve into this?

3 Think it would be ok to cut and paste the fuel rail to fit the different spacing?
 

·
Super Moderator
Joined
·
13,844 Posts
1 Do I cut the flanges off a 1.9 intake to use with the runners on this or do I cut the bungs and mounts and use more of the stock intake?

Might as well just use the flanges and keep the stock injector mounts from the new manifold.

2 How in the wide world of sports would you fit a cold start valve into this?

Well, if you want to use the Megasquirt, you won't need one. The stock injectors will handle the cold start fueling.

3 Think it would be ok to cut and paste the fuel rail to fit the different spacing?

No problem, could probably just use high pressure hose or tubing to extend or shorten the fuel rail.

Bob
 

·
Banned
Joined
·
3,842 Posts
Discussion Starter · #20 ·
I was thinking I'd use this Gm intake and cut it to make 1.9 flanges from it. I got the Intake for 30 bucks that included just about everything. The green lines are where to cut it
 

Attachments

1 - 20 of 110 Posts
Top