High compression N/A motor or turbocharged motor?

[Dan Dryden]

I'm specifically talking type 1 engines here and realise a lot of people will not have experienced both, but I'm trying to gauge people's preference when it comes to a performance Type 1 to be used in a street beetle with occasional circuit track use.

Things to consider:

• Street drive-ability / predictability/ power delivery

• Race circuit drive-ability / predictability / power delivery

• longevity

• simplicity / maintenance

• reliability

• Gas mileage

• Both motors would run efi

What would you choose and why?

[Chip Birks]

Definitely turbo, had a 14:1 motor in a "street car" years ago, it sure smelled good when standing behind it. But paying 8 bucks a gallon for fuel a decade ago wasn't economical. Not a pump gas engine at all, that engine was good for low 13s at my altitude. Same car later got a smaller, milder draw through setup and went deep into the 11s, pump gas cruiser, ran race fuel on the strip though.
Current car has a 9.1:1 turbo setup, weighs 200lbs more than the old car, gets better fuel mileage, and is faster and will do it on 91 octane or e85. Yup, boost will always win in my book. That said, if packaging is a question, i might consider pushing the limits on compression and CC, and staying N/A.

[ps2375]

Depends upon how high of a CR you go for. Personally I prefer an n/a motor, but boosted motors are "easier" to make more HP for the buck. But both take skill to build to make them long lived and perform as wanted. Ultimately it's your money and your car, lots of research will go far before you spend anything. GL

[petew]

I'm specifically talking type 1 engines here and realise a lot of people will not have experienced both, but I'm trying to gauge people's preference when it comes to a performance Type 1 to be used in a street beetle with occasional circuit track use.

Things to consider:

I reckon the best thing is to answer this one by one... I've owned 2 vws about the same hp in the end. One was a Subaru 2.5l (10:1 comp ratio) and the current one is a 1600 DP turbo. Both are/were EFI.

• Street drive-ability / predictability/ power delivery

NA; big, lazy and understressed/ Turbo; peppy, but a little laggy down low

• Race circuit drive-ability / predictability / power delivery

NA; slightly peaky, but smooth/ Turbo; actually pretty good and linear-ish once underload. Again this depends on the turbo you use. If you use your brain and go smaller (not bigger), you'll get insta-boost but run out up top. Again, this really depends on the motor and turbo.

• longevity

Both are/were internally stock so with good oil and no overheating I expect they'll last a long time. Where the turbo car is concerned moderate boost levels (not about 14psi) and good tune are more important. You've not said much about engine size you're intending or the like. That will effect things a lot, but suffice to say, good ATMO motors like big revs. Revs wear motors out over the long term. Turbo motors don't need big revs.

• simplicity / maintenance

The NA subaru was super simple to maintain. Change oil and filters and off you go. Of course with an ACVW you'd need to set the valves as well. Getting the turbo setup has been harder with ACVW motor, but then I might have had the same issues with any other motor. It's not a simple setup between the EFI, intercooler, oil and exhaust systems.

• reliability

I've definitely had teething issues with the turbo motor, but then that is my lack of experience as much as anything else. I similarly had teething issues with the subaru motor and I think you should expect them with a highly stressed ACVW motor too.

• Gas mileage

Well, how long is a piece of string? It really depends on your right foot. Although I will say, the tune will really effect things too. I did 27mpg (4:12 R&P) recently with the turbo motor driving a 375 mile round trip (with 98oct). I can't say for sure, but I don't think the subaru would have done that well AND if you're running big comp you'll need E85 and you can expect milage to drop drastically.

• Both motors would run efi

Given that it's the same price as decent webers now, that's a no brainer.

What would you choose and why?
Even with all the packaging dramas I've had trying to not cut a very original 50's car, I'd say turbo everything. Always turbo. Heck, if you've got a super duper atmo motor just drop the comp ratio down and it will be even better with a turbo, yet without stratospheric revs needed.

P.s. what hasn't been mentioned here is the way forced induction makes a motor more efficient. Obviously we're behind the 8 ball when we even start with ACVW engine architecture. I'm not saying a turbo fixes everything, but it does help side step some of the issues that make big revs/high flow heads easy on other engines. Which btw, is the same philosophy every OEM is using to build sport models these days. In fact it's pretty hard to buy any new VW without a turbo.

[madmike]

Use to run Dual Weber motors first with 44 IDF's , then I Modified them with the CB Up-date kits,, Better
swapped to the Big boy's 48 IDA's sifting @8000 rpm with expensive close Ratio Gear box's,, beat a lot of V8's up here 20 MPG was best
my son kept telling me to go 'Turbo' (Honda kid)
well he was right ,, once I went turboed , won't go back to N/A
no more sifting @ 8k (5-6k worx good,,,
stock ratio transmission's work AWESOME
Pump gas have gotten 28mpg with a 750 Demon 4 barrel without airfilter

[4agedub]

https://www.youtube.com/watch?v=d6GYj_5IWi4&t=16s
Reliability of the turbo engine you ask... check the vid.

[Dan Dryden]

Thanks for your response everyone!

4Age Dub, I love that video link you posted!

I wanted to keep responses as open and unbiased as possible, which is why I neglected to specify finer details such as capacity and size of turbo etc.

I already run a 1776cc type 1 efi turbo engine and have been for 10 years (first 5 years on dual dellorto carbs and then switching to EFI).
Further development is needed on the cooling, which I will be working on over the winter months - mainly moving components into the path of better airflow and better use of ducting - but that is not why I'm asking the question.

The reason I asked the question was this video:

https://www.youtube.com/watch?v=SSPaixMKJSc&t=9s

This was an event which took place earlier this year. Some in-car footage can be found here:

https://www.youtube.com/watch?v=CH2wwz9YFV4&t=556s

These cars are mainly German-owned, with large capacity, high compression, high revving engines. They handle magnificently and certainly have plenty of power. I was wondering why they seem to favour N/A engines over turbocharged. Perhaps there is something I've been missing?


The reason I mentioned gas mileage was purely to settle my own theory.
A friend of mine runs a 9.5:1 compression NA 2109cc engine with FK8 cam and CB 044 heads on dual Weber 44IDF carbs.
My engine is 1776cc, 7.5:1 compression turbocharged (21psi full boost), CB 044 heads, TCS 10 cam, single 48mm throttle body on EFI management.
We both went on a road trip in our cars, which are similarly geared (my gears being slightly taller due to larger wheels), but his car was far better on fuel than mine.
My theory on this was that his high compression gave a more complete burn whilst at cruising speed, whereas mine was running little to no boost and therefore only 7.5:1 compression for most of the journey, making it far less efficient. - Anyway, I'm fully aware that performance and fuel economy don't come hand in hand, it was just food for thought.

[petew]

I was wondering why they seem to favour N/A engines over turbocharged. Perhaps there is something I've been missing?

What you're missing is mega $$$$$$$.

The reason I mentioned gas mileage was purely to settle my own theory.
A friend of mine runs a 9.5:1 compression NA 2109cc engine with FK8 cam and CB 044 heads on dual Weber 44IDF carbs.
My engine is 1776cc, 7.5:1 compression turbocharged (21psi full boost), CB 044 heads, TCS 10 cam, single 48mm throttle body on EFI management.
We both went on a road trip in our cars, which are similarly geared (my gears being slightly taller due to larger wheels), but his car was far better on fuel than mine.
My theory on this was that his high compression gave a more complete burn whilst at cruising speed, whereas mine was running little to no boost and therefore only 7.5:1 compression for most of the journey, making it far less efficient. - Anyway, I'm fully aware that performance and fuel economy don't come hand in hand, it was just food for thought.

Do you know what you're milage was?

Also, what are you're cruise AFRs? That will have more effect on your milage than anything else. Piledriver had me tune my car for cruise AFRs of 17.

Show us your AFR table. Here's mine...

PDsupgrades AFR draft 1.jpg

I'm using the same cam as you BTW.

[Dan Dryden]

Hi Pete, I don't currently monitor my AFR's. My car was tuned professionally, so it has pretty much been set and forget.
The road trip was around 3 years ago, but I think I averaged around 28mpg.
What do you think of the TCS10?
I would definitely build my engine differently if I were to do it again. The biggest changes would be a higher compression of around 8.5:1 and an FK8 cam with 1.4:1 ratio rockers. - I think this would give me some more "pep" off boost and also an extra 1000-1500rpm.

[petew]

Hi Pete, I don't currently monitor my AFR's. My car was tuned professionally, so it has pretty much been set and forget.
The road trip was around 3 years ago, but I think I averaged around 28mpg.
What do you think of the TCS10?
I would definitely build my engine differently if I were to do it again. The biggest changes would be a higher compression of around 8.5:1 and an FK8 cam with 1.4:1 ratio rockers. - I think this would give me some more "pep" off boost and also an extra 1000-1500rpm.

Not to criticize, but I always have my AFR gauge on. Additionally, not to criticize, but some of the best tuning you can do is closed loop on road driving with an autotune function like MS has. Dyno sessions can iron out kinks and tune the top end, but even factory ECUs tune themselves as you drive using AFR targets.

Over all, I'm reasonably happy with the TCS-10 given how close to stock my motor is. I do however, share the same frustration you have re ratio rockers. I only discovered I couldn't use them when I had the motor worked on recently. It became clear even 1.25:1 rockers don't work (and aren't designed to work) with the TCS cams. I will say though, changing your AFRs and your timing will help the motor be less laggy. I find my motor reasonably peppy down low.

[Chip Birks]

I ran 1.25s with a TCS20, no problems with setup or anything. What did you guys struggle with?

[petew]

I ran 1.25s with a TCS20, no problems with setup or anything. What did you guys struggle with?

The geometry was causing spring bind. I had double valve springs going in, but my engine builder and the head specialist were concerned about seat pressure as well as the bind.

[petew]

Well that's weird. I just looked up this...

http://www.englecams.com/downloads/2010 ... atalog.pdf

Page 27. Top of the page specifically says 1.25:1 rockers. Hmmmm....

[Dan Dryden]

Well that's weird. I just looked up this...

http://www.englecams.com/downloads/2010 ... atalog.pdf

Page 27. Top of the page specifically says 1.25:1 rockers. Hmmmm....

Yes, I've always been aware that the TCS10 can be used with 1.25:1 rockers but stick with the same 1.1:1 setup that my engine was mapped with. The reason is purely to protect my bank account, because professional mapping sessions aren't cheap!

When I originally set up my EFI 5 years ago, I did it on a shoestring and can see the value of running closed loop with an AFR target table. I may look into upgrading this over the winter. - It will also mean that it will "learn" to adjust the settings if I then upgrade to 1.25:1 rockers.
I imagine that because I'm running open loop, the tuner probably mapped it quite conservatively, which would explain my less than satisfactory MPG.

[petew]

Chip, I've got HD single springs. Would that be sufficient for 6k and 1.25:1 rocker?