Opel GT Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
60 Posts
Discussion Starter #1
Has anyone here done a turbo mod on thier GT rather then rip out that crazy little 4 banger and drop in some monster v8 and cut up the car. I would like to pep mine up a bit without going to far from the stock stuff. Is this a reliable way or would it be more pain then it is worth.
 

·
Registered
Joined
·
141 Posts
Turbo installations are, in some ways, more complex than the V8 swappie.

The issues are:

Heat
Durability
Setup

HEAT

A turbo installation uses exhaust gases to 'boost' inlet pressures above atmospheric. In the process, the 'squeezing' of the intake charge increases its heat proportional to the increase in pressure. This waste heat has to be dealt with - typical operating temps inna turbo motor are much higher than in a normally aspirated motor, which brings us to:

DURABILITY

The stresses imposed by a turbo can be significant. A typical boost pressure is *approx* 0.4 bar, or 4/10th atmosphere, or 5.88 PSI. This will increase the stresses on the moor by 40%, as the intake charge now is available for cylinder filling at atmospheric + 40%.

At this level, your motor better have forged pistons, and be built to take the extra load. NEVER EVER attempt to turbocharge a stocker motor - it won't handle it for long!

SETUP

This section could take 30 pages to do right. As with a normall aspirated motor, setup is EVERYTHING. The difference between a poorly setup turbo motor and a normally aspriated motor is the latter simly runs bad, while the former becomes a cast iron grenade - they blow up in a major sort of way!

A story:

Was working on a dyno setup for McLaren Engines some years back while they were testing a then-secret 1000 HP turbo 350 (built from a 454 block) All went well until the air/fuel ratio computer puked during a WOT durability test, and;

The biggest piece of the motor left after the explosion was the crank flange bolted to the dyno. The rest was scattered about the test cell - including some cast iron chunks embedded in the cement block wall.

Turbos only really work well when they are matched up with an air/fuel ratio computer that contantly compensate for the additional volume of mix going thru the motor. Back when turbocharging was popular as an aftermarket deal (in the early 80's), one magazine did a test of carburetted turbos - over 30% of the aftermarket systems grenaded their motors after a minute of WOT application.

Okay - having said alla that, what kinda HP can you expect?

Well - the engine must be de-rated first to handle the extra load without preignition. This entails lowering the compression ratio and going to a 'blower grind' (read mild) camshaft configuration with minimal overlap and a slightly reduced duration.

The base motor will clock in at say, 80 dyno HP. The application of boost pressure is fairly linear - you'll see approx 30-35% more power out of the extra 40% boost pressure - assuming the engine can process the extra flow. Porting and carb/FI setup is critical here.

The result? Not much more than you'd out of a normally aspriated 'hottie' motor - 104 dyno HP, or 125 'street' (advertised) HP.

I did a 2.2 normally aspirated Shelby for my brother using a build sheet nearly identical to Rally Bob's specs a number of years back. The normlly-aspriated hottie 2.2 was actually FASTER than a stock turbocharged version of the same car - it got off the line faster and mangaged to stay out front once it got there!

IF one was to get REALLY trick with w some slick closed loop mass airflow monitoring coupled with an evaporative cooled air-to air intercooler and knock sensing, it might be possible to break the 200 dyno HP mark - just don't expect the motor to last very long! The stresses would be HUGE - the rings and bearings would be as disposable as Kleenex, and the bugger will run the high side of 8 grand when you're done.

I can't stress this enough - it's ALL about setup. A well set-up stocker will outrun somebody's poorly set-up hottie motor - I've seen it happen over and over! Getting HP from an Opel motor is not impossible, but requires some careful forethought - it's not like going to the speed shop an ordering up a balanced/blueprinted/bored/honed w/torque plate .030 over 4 bolt smallblock Chevy with a .410 lift 272 duration hyd cam, small chamber Dart heads with 2.02 intake/1.60 exh valves, roller rockers and such that will turn 325HP with a set of Heddman headers, 650 Holley and Edelbrock Victor Jr manifold.

Any kid with a catalog can build that motor. Opel guys gotta think about it to get there from here. More fun that way.
 

·
Senior Contributor
Joined
·
903 Posts
There's no reason you can't gain substantial horsepower with a Turbo. Just don't expect to do it with a carb!

I've seen dyno sheets around 200hp from turbo 1.9's. As well as another CIH over 300hp but I don't recall the displacement. At leaste one person is currently trying to hit 400hp. RallyBob has an engine or two that are 'in progress' expected to be somewhere around 350 HP. I don't recall the specifics. Building the bottom end to handle these HP's shouldn't be that hard actually. You just have to do your homework and have some cash to spend. The opeltuners web site is a good place to start
-Travis
 

·
Registered
Joined
·
141 Posts
It's possible to build a limited-duration 400HP Opel motor - not much will resemble the stocker, nor will it be able to handle the HP for more than, say 10 seconds at a time.

There's a big difference between street HP, track HP, and strip HP. The build criteria are different for each application.

The 'bolt-on' turbo kits are scary - not scary fast, mind you, but scary in the fact they are touted as bolt-on Nearly every engine variable changes when a turbo is used - simply bolting one on is a recipe for disaster unless these variables are taken into account.

The only way to prevent disaster is to keep boost pressures to a minimum - preferably within the safety margins built into the motor. This is where the 6 psi cap comes in - most stock motors will withstand 6 psi boost without grenading.

With the advent of computer-controlled engine systems, Chrysler modified this to its practial limit on street motors - 10 psi boost for seven seconds, then 7 psi afterwards.

In any case, the laws of physics are inviolate. There's only so much displacement to take advantage of the positive pressure of turbocharging - hence the numbers drop out. I've seen this size motor on the dyno stands of GM's Tech Center, and 120-130 HP is the very best it's what it's gonna make at 6 PSI. Yes, it can be modified to make MUUCH more HP, but this is a very exotic motor - beyond the capability of the average motor builder.

Please keep in mind this is darned fast inna Opel - you'll be able to run with some pretty fast company!
 

·
Registered
Joined
·
60 Posts
Discussion Starter #6
Ok so it sounds like the turbo idea is shot..

My brother has a BMW 325E w/a turbo and wow you feel it move and the sound it makes when it accelerates (thats one wild ride). Hey maybe I'll have to get anouther GT and drop a BMW turbo motor&tranny in it...

Now any ideas on how I can get the most out of my stock setup.
Say tweaking my progressive Weber, speacial tuning? Electric ignition? Iv'e been reading alot of posts here and all over on tuning the weber to run smooth but not much in performance tweaking.
 

·
Member 1000 Post Club
Joined
·
1,520 Posts
Car and Driver put a turbo on an Opel back in the mid 70's. They went the low pressure, about 6 psi, route. The were looking for hotter performance coupled with improved emmisions. They were able to achieve BOTH. Someone on this list or the Classis Opels Group bought this car a year or so ago. If you wanted to go that route yourself, verses buying the set-up from TGSI, it might be a good place to start.

As long as you build it for a modest HP gain and take care of the small details, you should be able to expect reasonable durability.

Paul
 

·
Registered
Joined
·
141 Posts
There's actually a LOT about performance tweaking (tuning).

Take a day and read ALL of Rally Bob's posts...it's in there.

Just keep in mind there is no shortcut to HP. While on the subject, I thought of a story:

While driving my Shadow ES Turbo with a 146 advertised HP and a 5 speed, I had many encounters with SVO Turbo Mustangs. The later versions (1986) were rated at 205 HP. Since both cars weighed in at approx 2600-2700 lbs, the SVO shoulda eaten the Shadow for lunch, right?

Well...not exactly.

The SVO had a HUGE turbo (forget the model #) so as to post the big HP figure. Prob with the big turbo was inertial mass - took a long time to spool up. The result was like driving a car on nitrous - nothingnothingnothing waaHHAAA! Put your foot in the throttle in 1st gear on an SVO, and the tires will unexpectedly break loose at about 4500 RPM. While it's great fun to drive, it's not street fast...

On the street, I'd pull about 2 carlengths on an SVO before the boost kicked in. Mr. SVO would get to my door - then he'd have to shift. In the process of shifting, he'd invariably lose boost pressure, as turbos like to be shifted like motorcycles - leave the throttle open and go thru the gears. Most car folks don't drive like that - never encountered an SVO driver that did, at least.

By the time boost came up in 2nd for Mr SVO, I typically had a three carlength lead, and the point was made.

tuning for the street does not always mean HP wins the day - setup does.
 

·
Super Moderator
Joined
·
13,576 Posts
Paul said:
Car and Driver put a turbo on an Opel back in the mid 70's. They went the low pressure, about 6 psi, route. The were looking for hotter performance coupled with improved emmisions. They were able to achieve BOTH. Someone on this list or the Classis Opels Group bought this car a year or so ago. If you wanted to go that route yourself, verses buying the set-up from TGSI, it might be a good place to start.Paul
As might be expected with turbos, the C & D car had its' boost turned up a bit higher, and ended up blowing all the rings out. The current owner Craig Roberts had to replace the shortblock because of this.

The problem is, carbureted turbos do not have very good fuel atomization. In fact, I'd completely put the idea of a carbureted turbo out of your mind. If you do a draw-through system, the carb can remain stock, but you can't intercool it.

If you go blow-through, you can intercool it, but then you will be pressurizing the carb. So, you will either have to build a leak-proof box around the carb, or re-engineer it to be pressurized. It will leak air past the throttle shafts, and the power valve vacuum port will have to be repositioned to accept vacuum from BEFORE the turbo (or you will pressurize the power valve and force fuel back into the carb....leaning it out under boost), and you will need to use a rising-rate fuel pump/regulator. If you have a fuel pump with 5 psi fuel pressure, and you boost 5 psi...you will cancel the fuel pressure out, forcing fuel back into the fuel lines. You want to have a pump capable of feeding fuel pressure that is as high as your boost levels are, PLUS the fuel pressure the carburetor need normally (3.5 psi for a Weber).

Another concern is older distributors have WAYY too much ignition advance...you'll pop a motor in no time if you have the 'wrong' distributor for a turbo. Also, a higher energy ignition is mandatory. An ignition has to work much harder to strike up your plugs under pressure.

In my opinion, the only way to go is with fuel injection. However, I would NOT use the standard Opel fuel management. It is woefully inadequate for a turbo application, at least the older analog L-Jetronic fuel injection. I am building a turbo engine for my Ascona wagon. I am using the 1975 fuel injection intake manifold.....that's all. The rest will be custom. I will have injectors that are over 80% larger to handle the increased fuel requirements of a turbo. I will have a larger capacity fuel pump (110 litres per hour), a larger (custom) fuel rail to feed the injectors, a larger 65 mm throttle body adapted to the stock intake, and a stand-alone programmable ECU (this eliminates the stock restrictive MAF).

Besides the changes above, I still need the turbo, the wastegate (integral), a custom exhaust manifold, a custom exhaust, an intercooler, intercooler tubes and silicone connectors, a blow-off valve (not necessary for low boost applications but a good ides nonetheless), a larger radiator to help with heat dissipation, an oil cooler, a modified oil pan for the oil drain-back line for the turbo, etc, etc.

Initially, I'll be installing all these components on a stock 1971 engine with very low mileage. I KNOW it will pop eventually, I'm simply curious as to 'when' this will happen, and it is a testbed for the operation of the fuel/turbo system until I can build a proper reinforced shortblock and a better cylinder head with stainless valves and adequate valve springs.

My goal is to put around 10 psi of boost into the modified engine, with the capability to run 15-16 psi as needed. This should net me around 260-275 hp reliably. HOWEVER, be forewarned that it will not be inexpensive to undertake something like this, and there's a lot of fabrication involved. My estimates so far are $3100 for the turbo stuff and management (the turbo is dirt cheap because I got an almost new turbo and intercooler from a friend, otherwise add another $1000 to that figure). It'll cost me another $1400 for a short block (all my labor), and another $1200 for the top end of the engine (again my labor). Then there's all the turbo manifold/exhaust/intercooler fabrications.....my labor, but if you paid someone for all the engine labor, fabrications, programming, dyno time (I also get dyno time for free), and didn't get a deal on the turbo, it'll cost about 40% more than my prices.
This is NOT cheap to do, but if you go the cheap route, then pop the motor, then build a new one, then pop it again....which one makes more sense to do?

Bob
 

·
Registered
Joined
·
141 Posts
Yeah. what he said.

There is no shortcut to big HP gains - it's all about hard work and a fair amount of $$.

A vehicle is a complete mechanical system - make a change to one element, and it WILL effect EVERY other element in the car.

illustration by example:

My then girlfriend (now known as the Peebmonster) had one of those nasty Omni 024's. After about a year of ownership, the car began to run rough. Her dad, a notorious cheapskate, decided he's save a buck by turning up the idle speed. As the car would begin to miss, he'd add a turn or two on the idle screw. By the time I began going out with her, the car idled at 4000 RPM.

Idle speed's no big deal, right?

Not really.

Th car cruised around town at 40 MPH - no throttle. Brakes were replaced twice in a year. Exhaust system failed at the manifold from the stress of the engine torquing as the car was put in 'drive'. $500 spent on new brakes and exh.

But...We're not done. A month later, the front engine mount shears. I've seen broken rubber mounts, stripped studs - but never a clean shear - until this 024 came along. Replaced it.

A week after that, she pulls into the apartment parking lot with a motor that's clattering to beat the band. I look at the gauge cluster - the engine light's on. "WHAT WERE YOU THINKING?", I yelled after she said she drove it ten miles that way.

"I saw the light and thought, yeah - I have an engine!"

Sheesh.

Upon teardown, it was discovered the inertial load and shock of the 'klunk' into drive from 4000 RPM sheared the oil pump drive.

Another $500 in parts.

Ten days after getting it back on the road - ka-WHAM! big bang - the engine runs - the car won't move. Teardown the transmission - countershaft bearing grenaded. Yet another $500 in parts.

Soo...$1500 spent fixing:

Brakes
Exhaust
Engine
Transmission

All beacuse the idle speed was cranked up.

Now if that's what idle speed can do - imagine the effects of a poorly set-up turbo!
 

·
Registered
Joined
·
60 Posts
Discussion Starter #12
Are there any kits in the way of going to a fuel injection system. I can't remember but I thought OGTS sold or used to sell a fuel injected engine. I figure this is safer then turbo for an inexperinced Opeler as myself. Did any of the later Opels have fuel injection?
 

·
Super Moderator
Joined
·
13,576 Posts
If you read my post above, you'll see I commented that the Opel factory FI is really not suitable for a turbo application. It's not mapped for it. Early Opel FI was analog, so it's truly no mappable by today's standards, but even the later FI (such as what OGTS sells) can only handle limited boost applications. The injectors max out at around 180 hp, and the stock MAF will lean out at higher rpm/boost loads. You could probably get away with 5-6 psi boost with a stock engine, but that's about all, safely.

For anything crazier you'll need a programmable FI system. Those prices range from $700-$5000 (median pricing seems to be in the $1100-1600 range), but this will be the basic harnes and ECU only. You'll still need a manifold (the 1975 Opel is a good donor), the injectors, the fuel rail, the throttle body, the pressure regulator, the fuel pump, high pressure fuel lines, baffled fuel tank, and the various sensors (some ECU's allow the use of stock sensors). You'll also need access to a laptop PC for programming, and either a good knowledge of engines and a lot of free time, or access to a dyno. Detonation or running lean is NOT an option with a turbo. Ten seconds of 'pinging' in a stock Opel is an annoyance....ten seconds of pinging in a turbo car is a broken engine. The pistons will be junk.

Bob
 

·
Senior Contributor
Joined
·
903 Posts
There are viable alternatives which will help to save a good deal of money here. Although not the the most sophisticated system available, Megasquirt should be adequate for a basic turbo system. This will get you a CHEAP mapable FI system.

True wide band O2 sensing has become available over the last year and at an affordable price. DO NOT waste your time and money on the systems you see in the catalogs. They are junk. For ~$600 you can have very accurate wide band sensing including a calibrated sensor and exhaust back pressure compensation. This is critical in a turbo motor. This will be money well spent!

And then for the ambitious people there are lots of doner cars in the local junk yards with turbo parts. They may not be the latest and greatest parts, but they will work well if chosen properly.

-Travis
 

·
Super Moderator
Joined
·
13,576 Posts
More data Travis! Are you saying that the cost of a complete FI management WITH wide band O2 is +-$600, or are you saying the cost to retrofit an existing ECU is $600? Sources? Just curious, as I'm still in the 'parts collecting' stages right now, so I'm not dedicated to any particular brand/model. I was leaning towards a DTA system, as my friend has this in his turbo Golf rally car. Pretty neat system.

Bob
 

·
Registered
Joined
·
60 Posts
Discussion Starter #16
What I meant Rallybob is rather then go with turbo at all, is look into a FI set-up alone no turbo charging. I think this post has proved that turbo on my stock 1.9 is a bad idea. So my other alternatives are tweaking the hell out of my Weber, Fuel Injection, or dare I say Dual Side draft setup. I think setting up fuel injection may be over my head same with the Turbo, so that leaves the Dual side draft option. Any more wisdom from the masters. The whole Dual side draft option kind-of scares me it has taken me (new opeler) 2 weeks to work all the kinks out of my Weber much less 2 of them.
 

·
Member
Joined
·
149 Posts
I just recieved an advertisment from Opel GT Source that says they have DOHC 2.0L 16V engines for sale. Includes 5 speed Getrag, clutch EFI manifold, harness & injectors, Motronic ECM, MAF, Alternator, Starter, Crankshaft pully and flywheel. Stats are 204 HP @ 5600 rpm & 206 ft. lb. of Torque @ 2400 rpm with 36mpg.

Darrin
 

·
Senior Contributor
Joined
·
903 Posts
Bob,

Megasquirt is a simple batch EFI system whose design has been made available on the net. Heres a little burb

--------------------
The MegaSquirt itself is a build it yourself programmable EFI controller that costs about $110.00 and requires assembly. Its home page is http://www.bgsoflex.com/megasquirt.html

The second group buy Is Now Closed! We will re-open the Group Purchase in middle September - be sure to check this site for information on this. [The group buy operates by pooling everyone's funding together, then ordering all components in one order, thus obtaining quantity discounts for components, which keeps the overall cost very low.]
--------------------

http://www.egortech.com is where to look for wide band O2 sensing. They have a hand held meter which is well worth looking at. It can be interfaced with the megasquirt but as it's hand held it's a little bulky. There is another company which egortech is close with that they will refer you to if you'd prefer a non hand-held system purely for use with an EFI system. If you have any questions about 02 sensing Garfiield Willis at EGORtech is the man to talk to. I've been soaking up his knowlege for quite some time now on another list and he really knows his stuff. They get $397 for their basic unit. You can buy the sensor from them with calibration for $200 or buy it yourself for $125. This is the same exact sensor Motec is selling for $500. ..used on the early 90's lean burn honda motor.

-Travis
 
1 - 20 of 24 Posts
Top