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Opel Bolt on Turbo

8782 Views 8 Replies 6 Participants Last post by  kwilford
Does anone have any more info on Bob Dennard of TGSI racing´s turbo kit ? You can see a pic at www.tgsi.com/opel.html. I wrote him and he says it uses the 32/36 or a 38 DGAS Weber on the stock intake manifold and puts out 7-1/2#. Good for 40-50% increase. I was looking to have a hot street head built, but at $1750, the turbo may be a better bargin.
Any thoughts or more information?
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I would question the use of a draw-through turbo with carburetor on a used Opel engine. I've tried it before, but the standard Opel intake manifold does not have great air/fuel distribution, even with a carburetor bolted to the intake. Increasing the distance by placing a turbo between the carb and intake makes this worse. I'm not saying it won't work, it will, but you're about at your limit boost-wise. You can't add an intercooler on a carb'd setup either, and the stock low compression pistons are notoriously weak at the ring-land area. I'd be surprised to see much more than 30-40 percent increase in power, which means that a smog-era Opel (gross) 1.9 would go from 75 hp (gross) to about 100-105 hp. Also, sustained high speed driving will DEFINITELY require an upgraded cooling system, turbos create unbelievable heat.....enough heat to catch anti-freeze on fire, and that stuff does not burn easily!

I suspect that unless you start with a new rebuilt engine (new pistons definitely) and very careful setup (impeccable tuning of the air/fuel mixture and re-curving the distributor, plus and GOOD electronic ignition, there will be reliability problems and potential engine failure. In this day and age, the only way to go with a turbo is a stand-alone programmable fuel injection system.

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blow through turbo

Actually that particular turbo "kit" looks to me to be a blow-through type, so it doesn't even move the carb from its stock location. If that is the case, it could be modified for an intercooler, and probably should be, and all of Bob's great porting tips should still help too.

Blow through turbos set-ups and Weber carbs require careful set-up and maintenance. The throttle shafts on the low-end Webers are prone to leakage, and the high end ones use ball bearings on the throttle shaft that require some modifications to install a satisfactory seal into. Some tuners prefer Webers because the fuel bowl vent and the venturi inlet are usually machined on the same plane, making for easy fabrication of fittings. Just spend a little time looking for VW sites and you'll probably get more info on blow through turbos than you could have imagined.

Another possibility might be a fuel injection set-up with that turbo kit. Opel EFI manifolds aren't that difficult to get, and with a little clearancing to get it into a GT, you would have the majority of the hardware. There are also several manufacturers of quality stand alone EFI setups.

Also, just like Bob said, remember that a turbo isn't something you bolt onto a tired engine. The power they can help an engine make would certainly kill a poor condition motor. You will probably have to drop compression ratio down unless you plan on running JP-5 as well. Cooling and braking systems are also must-haves
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It's just a pleasure to read the quality of imput on this site. And awesome to know that it's all right here to help on even everyday problems. You guys are great!
What Rally Bob has told you is essentially correct. First, you can't add performance to a "tired" engine. This goes for any performance mods. If you add as little as 15% and then use it, your engine is likely to expire. It doesn't matter how you get the improvement... turbo or otherwise.

Heat/marginal radiator is also a problem... on any Opel. Out here in the South West, a stock un-modified Opel with an old radiator has problems with a run to 'Vegas in the summer. This is one of the first upgrades you need to do for any performance increase. Ignition up-grades are also in order for any performance increase. Again the stock stuff is only good for stock. Any performance enhancement requires a good ignition.

I've had this basic information on my web site http://www.tgsi.com/eng1.html for years. Read this before you do any other mods. Also read http://www.tgsi.com/eng2.html (Sorry the web is such a mess, but we're working on it.)

We are using a "suck-thru" approach, not a blow thru. It will make a 40% - 50% increase in HP without spending a fortune. I'll repeat... DON'T DO THIS ON A TIRED ENGINE... no matter how you try to get it... it will go BOOM. The reason we are using "suck-thru" is cost and ease of installation. We have built "naturally aspirated" performance engines for years. The cost of a 40%-50% increase in performance for a "naturally aspirated" engine is about twice the cost of the turbo approach.

We have designed (but not yet built) a FI turbo system. We have not built it because we don't think we will sell any. Here's a few items of additional cost for a "warm-up"... Intercooler ->$500 (new custom HI-flow unit)... Engine Management Computer (Opel FI unit won't do) -> $1250, RC Injectors -> $400... That's over $2000 just for warming up. The whole system will cost $4500-$5000... not including the cost of the clutch, transmission and everything else to support what the system could make. Somewhere else on this site, Rally Bob has outlined the cost to make a full tilt system survive... so like I said, we don't think we will sell any.
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Ported Intake

Is the ported intake per RallyBob's instructions considered a bolt on? After reading through TGSI's detailed upgrades, I was sorta surprised not to see it on the list of bolt on upgrades.

Thanks for all the information, from both RallyBob and TGSI
I'm not sure that Rally Bobs intake mods classify as a bolt on. It takes a little extra equipment beyond the normal wrenches everyone has. It is not in my "first things to do"... well 'cause it's not one of those first things to do. (Also because I wrote/posted that stuff before Rally Bob "published" the info.)

HOWEVER, if I ever get around to writing "201", it will be first on the list... that is if you are going to stay with the original manifold. In any case, Rally Bobs intake mods will make the turbo set-up better... it will make anything that bolts to the original manifold better... maybe even the Solex. Ok, maybe not the Solex.
Yup, even the Solex! In fact, a ported intake with Solex makes more power than a non-ported intake and a 38 DGAS Weber, it's that important. Of course, this was with a modified Solex (increased primary venturi to same size as secondary, and re-jetted it accordingly). For a true *stock class* circle track car I helped a friend build.

Yet another fine thread rejuvenated. These later threads came with the order intact, and even user names...
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