D-Jet or Carbs - what would you do?

[nhallman]

After searching the numerous threads on this topic (and reading pbanders D-Jet vs. Carbs web page), I'm probably more confused than ever. So, I'm posing the following scenario as a "what would you guys do in my situation?" question. I'm probably naive to think that I'll only get one opinion out of this...

Here's the scoop:

1. I own a '75 1.8 with L-Jet.

2. I just purchased a running '74 2.0 motor that is completely stock except for a carb conversion to a single Weber with "bugsprayer" manifold. The D-Jet system is long gone. I plan to replace the 1.8 with this motor, but I may change the fuel delivery first (which is the heart of my question here).

3. I want more than the stock 95 hp, but I also don't want to make any mods that don't conform to SCCA Street Prepared rules. This car is a driver but it is primarily my autocross car. For those of you unfamiliar with Street Prepared, the relevant rules to this topic are basically:

a. can't change the cam
b. fuel system is free (injectors, carbs, whatever)
c. ignition, intake and exhaust are free
d. displacement of the motor can't be changed (OK, yeah, there's like 1.2 mm overbore allowed, but forget it).

4. I'm no FI expert, so the Megasquirt seems a little daunting. If I knew of a reliable setup out there somewhere, I'd be willing to entertain the idea of trying MS, but I don't want to get in over my head.

5. I'm on a budget.


So...

...should I be shopping for a D-Jet system? How much will that set me back?

...should I leave the 2.0 as-is? Is there *any* carb setup that works decently with the stock cam? I hear that HP decreases if carbs are used on the stock motor, if so that's heading in the wrong direction.

...do I have a hope of properly installing a MS system, with limited FI and electrical knowledge?

...will I have electrical system issues with putting the 2.0 into the 1.8 car, esp. if I go back to D-Jet?

...obviously fuel system alone doesn't make performance, but what will be most compatible with other mods I have in the works, like MSD, points-less ignition, Kerry Hunter headers, etc.?



Sorry for all the questions... like I said, I'm pretty confused at this point and I don't have the time to make (too many) mistakes on this project...

--Nick

[Alfred1]

You could wait for Kit Carlson's system to come out - he's currently testing it in someone's 914. Someone else (DNHunt?) built a Megasquirt and added up the costs and said it's not as inexpensive as it initially seems. Also, checked the classifieds - maybe you can find a complete d-jet system for your motor for a fair price.

[anthony]

With the stock cam I think both carbs or djet can be tuned for maximum horsepower. A full D-jet setup, if you can find it, should run about $300-400.

I think a brand new set of dual carbs runs about $600 at CB Performance.

Another possibility is using L-jet. Maybe Mueller will chime in. He ran ljet on a 2L engine.

[nhallman]

With the stock cam I think both carbs or djet can be tuned for maximum horsepower.

Dual carbs, I'd assume, not the single-carb setup I have now. Out of curiosity, what kind of drop in HP should I expect with the motor's current setup, assuming everything else is in good shape?

Another possibility is using L-jet. Maybe Mueller will chime in. He ran ljet on a 2L engine.

Really? This is interesting, since I obviously have a working L-Jet system right now... again, what kind of HP are we dealing with?

[Jake Raby]

Carbs........

[nhallman]

Carbs........

Even with stock cam?

[Bleyseng]

The key word is Autocross car. The Djet or Ljet will out preform any Carb setup for AX. They both provide the maximum low rpm torque you need vs a dual carb setup.
I am way more familar with Djet as I have setup my car with that and AX alot.
I know you can get the Ljet to work also.
Since you can't change the cam the dual carbs will decrease the performance of the engine as the stock cam is setup for the Djet.
First- make sure this 2.0's valves are in top condition renew them if they are marginal.

Second-I would install the FI and tune it on a dyno after spending the money on a CFR header system. You should be able to get 90+ hp to the rear wheels with that header.

Drive the heck out of the car and enjoy it as this is a momentum car and hp is not that important.

[Dave at Pelican Parts]

The first question here is, do you know carbs? Know how to tune and jet them, know what works for them? You have already stated that you don't know FI all that well. If you know carbs much better, then put on a set of dual Dells and go.

If you don't know carbs that well, then you are going to have to educate yourself on some kind of induction/fuel system. I think FI would be the better choice in that case. The L-jet would be simpler in some ways, but the air flow meter is restrictive.

That brings up the next point--power. How concerned are you about making the absolute most power? If you absolutely have to, then I feel an aftermarket adjustable EFI is the only option. Most of them are $$$$. Megasquirt is less, but you have to work out a whole lot of details yourself. And it may be that throwing out the FI manifolding and using dual throttle bodies with your injection system will give you the most power--I haven't seen positive results the one way or the other, but it makes some sense that way.

If you can fiddle and tune the carbs correctly, you should be able to convince them to give you pretty much the same amount of power as the stock-type FI. They are usually going to be unhappier with changing conditions (temperature, humidity, cold start, etc.), and you may run into float bowl sloshing problems in the longer sweepers. Probably not for autoX, but on a road race course the corners are longer.


So my advice is: Go with what you know. If you don't know any of the systems, pick one and learn it. (I suggest aftermarket FI in that case.)

Oh, and second the recommendation for CFR headers. K-H is good, CFR is better. And costs like it.

--DD

[nhallman]

Carbs I know. FI knowledge is limited to troubleshooting the L-Jet on the 1.8. I wouldn't call it a comprehensive knowledge.

I am confident I could get the carbs working about as well as carbs will work on a 914... the question is, is that really good enough compared to what I could do with a good FI system? Especially since I'm leaving the stock cam in there.

My question on the header is - can the CFR header really be worth paying almost $1000 more than the KH header? I mean, I know it's nice...

That brings up the next point--power. How concerned are you about making the absolute most power? If you absolutely have to, then I feel an aftermarket adjustable EFI is the only option.

I want to make absolutely the most power I can make without spending more time or money than I have to give. How's that for wanting my cake and eating it too?

Which aftermarket EFI's have you guys used... which do you recommend? Is Kit's system the best option?

[tat2dphreak]

go carbs!
if you know carbs, that's the best option... Kit's system is not out yet,

megasquirt is reserved for those who either really know FI or really want to learn... Dave is 100% right, put on some dells (or weber 44s) and GO! have fun!

[Jake Raby]

carbs.......

[nhallman]

Originally posted by Jake Raby
carbs.......

I think I'm seeing a pattern here...

[norustscott]

Jake,


Even with a stock cam...no other changes to the engine? the carbs wil out perform the stock djet? Power, Mileage, Cost, Maintance?


hmmmm.

[Alfred1]

I just purchased a running '74 2.0 motor that is completely stock except for a carb conversion to a single Weber with "bugsprayer" manifold.

There is something to be said for originality so if it were me, I would look for a good d-jet system to put back on. You can test most of the d-jet functions with just a DMM.

[Jake Raby]

I have a complete D Jet system from my car. It was running ok when I pulled it off. It has new injectors and all new fuel hoses.

I like carbs much better........ Thats why I swapped!

[norustscott]

I am in your camp too. The question has always been whether carbs can match the Djet performance with a one to one swap... on a stock motor. In other words the cam and valve train left stock.

[Dave at Pelican Parts]

I think they can match it, or at least come "close enough". Most carbs straight out of the box are not set up very well for our cars, and will definitely lose power. But if you can set them up well, they should give you very similar results.

--DD

[anthony]

I think the easiest thing here would be to find a stock D-Jet setup. "Out of the box" it should work great. With carbs or megasquirt you really need dyno time to tune the setup to the engine for maximum power/efficiency. It's easy for Jake to say carbs since he has extensive knowledge with them and a dyno that he can use to precisely dial in an engine/carb setup.

[pbanders]

If you're doing the motor for an AX-specific car, the optimal fuel system would be an adjustable aftermarket FI system, cost no object. Carbs cannot provide the precise metering over all running conditions that modern FI systems do - if they could, that's what auto manufacturers would be using.

If cost is an object, for an AX-specific car, dual carbs would likely be a better solution than D-Jet, as the tunability of D-Jet for different VE curves than stock is limited (since you can modify intake and exhaust, your gains will come in better VE). It might not be as good as a FI setup, but will likely be pretty close.

[sean_V8_914]

Hmmm...many good points for carbs. I was weened on Chevys with Holleys, Rochester Quadra-bog and even a few Carters. I had a 1.8 L-Jet. after 2 months, much effort and learning, I got it to run really well. Info found on vw bus sites. It ran for nearly 5 hard years with only valve adjustments needed. Much spirited driving and AX killed it. Then I put in a 1.7 with D-Jet. That was easier to get working due to Brads most excellent D-Jet shrine (web page). I liked the way the L-Jet ran; better than D-Jet. Fellow Pelicaneers in So Cal can attest to the flogging I gave that 1.7. It only takes an hour to test your FI parts before you put them in.

ohh...I vote for FI

Kenny in San Diego runs a 2.0 L-Jet

912e was L-jet with green injectors and fatter intake runners