1915cc Performance Improvement Question

I have a pretty standard 03 Vintage with a 1915, 3:88, dual carbs, an external oil cooler and a deep sump. The car pretty much tops out at 80mph at around 4000rpms, and that's pushing it hard - I rarely drive faster than 70mph at 3400rpms.

I would like to be able to cruise at 80mph at about 3400rpms so that I don't feel like a hazard on the freeway. What can I do to improve this engine's performance? Where should I start?

Thanks!
Brian

Put some taller gears in your transmission.

cruising at 80 MPH at 3400 has got nothing to do with your engine. It's a combination of the transaxle's final drive, (3.88) 4th gear (Probably .89 or there abouts) and your tire size.

If you have 205/60/15 tires, 3.88 final drive, .89 4th gear, 4000 RPM's equals 85 MPH.


Same combination at 3,400 RPM's equals 72 MPH. A 195/65/15 is only 1 mile difference.

Change the ring and pinion to a 3.44 and 3,400 RPM's equals 82 MPH.

Remember, the faster you go, and the more RPM's you turn, the more heat your engine developes and the heat requires more cooling air.

Cooling air is developed as the engine turns more RPM's. Kind of like a dog chasing his tail.

Slow the engine down via gearing, increase you speed and you have more drag or load on the engine, more drag/load equals more heat, more heat requires more cooling air, etc etc etc.

5,000 RPM's is roughly 107 MPH, 5,500 is 118 MPH.

You'll need a larger displacement engine to achieve the power to combat the coefficient of friction generated by your car, tires etc.

Next catch, more engine requires more cooling air because it naturally developes more heat. and on and on and on

Great posts. To answer your question directly on how to improve performance; get your heads ported or better yet get a set of ported big valve heads such as 40 by 35.5's. I also have a VS with a 1915 cc and I've been able to confirm that motor is basically a VW Mexico crate motor that's been taken apart, machined for 94 mm cylinders and put back together so in a sense it leaves a little to be desired if you're trying to maximize performance for the displacement. It will definitely need to breathe better so the heads are the first thing to look at along with more efficient carburetion such as dual throat Webers or Dellortos and better exhaust (I installed Dellorto 40's and a Tri-Mil exhaust). Also, if you don't want to split the case to install a performance cam, as what happened to me, install a set of ratio rockers (you can even go up to 1.4 with the stock cam without any loss in longevity); I went with CB Performance's OEM VW 1.25's and added a Gene Berg rigid rocker arm set and chromoly pushrod set along with Gene Berg swivel feet valve adjusters. From what I've been able to experience until now (I now need to sort a problem with cylinder #2 not firing); the car feels like a totally different beast from what it was. It sounds and takes off totally differently with a lot more power and torque; it's definitely an exhilarating and rewarding experience after all the blood sweat and tears that go into it.

Jim, when you do the math, based on your tire size (195/60/15) and your ring and pinion gear, it appears that you probably have a .89 4th gear.

Using that gear in the calculation, 3,700 RPM's equals 87 MPH
3,300 RPM's equals 77 MPH

The up and down hill only comes into play if you have a slipping clutch.

Interesting, Larry. Thanks... I'm sure you are right. Seems like Henry told me the late model tranny he installed had the tall 4th. Anyway your numbers ring true from what I see from the driver's seat.

How long have you been into ACVWs? Both you & Ricardo seem to have a good knowledge of engine/transaxle stuff from the posts I've read.

Larry's R/P -Tire numbers are pretty close to what I am experiencing with a 3:44, 195/60, late model tranny.

In the pics below, my speedo is about 4-5 mph high at speed, and the tach is right on the numbers.

The first pic is in the Mojave.... slight uphill grade, the second is climbing towards Flagstaff a pretty good incline coming out of the Colorado River valley. (2005)

No point here, just adding info to an interesting thread.

I started messing with VW's in the late 60's. In the early 70's, I purchased the complete inventory from a VW shop that was closing.

I initially went there to score a deal on heads, cases etc. Jokingly, I said, how much for everything, he said $1,000 I said I'll buy everything if you'll throw everyone out and lock the doors until I return. He agreed, I gave him a 100.00 deposit and returned about 2 hours later with my friend and a 30+ foot rented bob tail truck.
We loaded up the truck 5 times from front to back, top to bottom with engines, transaxles, cylinder kits, heads, etc etc etc etc. The ABSOLUTE score of a lifetime. My garage and side yard was wall to wall VW parts.

Over the next 2 to 3 years, I built engines, sold parts and scrapped the junk and cleared approximately $40,000.

I turned this into a part time engine rebuilding business. I'd build a few engines and then do an exchange or outright sale.

I'd go to a cutomers home, remove their engine and install a rebuilt.

I also built engines for a dune buggy store in Orange, CA. The owner would put them on an engine stand, add some chrome and sell them when he sold a frame. When I was done with all the useable parts I still had a load of defective cases, pistons, cyliner heads, starters, generators etc etc. I sold all of the scrap for and additional $3,500 and the core generators and starters fetched me another thousand or so.

I also am the Administor for the www.Spyderclub.com board and I recently started a forum called Tips, Tricks and Knowledge, similar to the Knowledge section of this board.

In my spare time when I'm not at the sand dunes or travelling, I do repairs, modifications and tune up work for several Speedster guys and a whole bunch of Spyder guys.

Thanks for the nice flattering comments Jim; coming from the man who has put more road miles in a Speedster than anyone else it's an honor. I'm not as experienced as Larry but I've been involved with a few ACVW's and love them. I used to work at a local VW parts shop and machine shop back in the '80's and had a couple of cars. One was totalled by one of my brothers in 1986; the other one I sold in 1988. Fast forward to 2003; out of the blue and I don't know why I started browsing on the web for Speedster replicas, found this forum and became a member as well as in Speedstershop. In here I acquired enough knowledge on Speedsters to decide to go with a VS turnkey which I ordered new in 2004. All this time I've been involved in improving it and reading quite a bit on ACVW's I like to spread the knowledge to my fellow members. Because of this site I met Jjr who's a 5 minute drive away; we've helped each other out a lot with our cars in the course of these past two years so it's all been a blessing!

Larry, now THAT's experience. I will follow the thread on the spyder forum. Thanks for posting here on the Speedster forum. Impressive, Larry! Very Impressive.

Ricardo, I always enjoy your posts. As far as miles, there are plenty of owners ahead of me on that list (Rick Davis comes to mind, Dale Bates, Paul Harford, others). I drive mine, but my knowledge level is not even close to yours, Larry's and 90 of owners. It's nice to read posts here that do help guys like me learn something valuable.

Jim, If, as you believe, the taller .82 4th gear was installed in your transaxle, here's the computations.
195/60/15 tires, 3.44 R&P and a .82 4th gear. 3,700 RPM's equals 94 MPH

I'll be over here in the corner, eating my hat.

("Taller gears." I'm a damned genius! Why do you fellas - and Angela - even humor me? Theron, ban my happy a** from posting in the engines/mechanical section from now on!)

I couldn't agree with Cory more. To the real wrench turners - thanks for your patience with rookies like me. I know it's annoying sometimes, but we have to ask obvious questions to learn. When you grow up in the 80's and your parents had Hondas, tinkering doesn't exactly come naturally.

Brian

Well Brian; I was just out of high school in the early '80's and while Hondas were starting to make their mark I was still tinkering with my beloved VW's. I knew Honda was making good cars but I still preferred my VW's. I guess I'm just a walking anachronism; judging by my tastes in cars, music, hair styles, clothes and women (maybe go back to the '40's in that category if you count in Rita Hayworth.....what a FOX!!). If I'd had my way I'd lived my youth back in the '50's & '60's and I'd be retired and in my '70's by now.

Hey guys, remember the old addage "...it's better to keep your mouth shut and be THOUGHT a fool, than to open your mouth and remove ALL DOUBT!"

That refers to me and my mechanical knowledge!! LOL

Like I said, I learn something new everyday (and mostly from this website).

Peace - Out!

I'm more of a Ingrid Bergman man myself, but I agree, Rita Hayworth...yes, two please.

Brian

Spent my youth in the 50s and 60s. Used to drool over Rita, but Ava Gardner was the woman I fantasized over most...with her sultry semi-gravelly voice and half-droopy eyelids that made one wonder what she had on her mind. She had a thing for fast-living guys and ended up with Frank Sinatra. Mygod...what was she thinking of? She could have had ME !!

Didn't Frank also have a fling with Rita?...

I think he had a fling with half of Hollywood. Ricardo I know how you feel. I'm 30 years old and feel I was born in the wrong decade. But my choice would be Natalie Wood or Audry Hepburn

Chris, too bad that both of them have gone off to the Big movie theatre.

Natalie Wood was just gorgeous too; especially after she was a little mature (in her mid 30's). I saw an interview of hers in the '70's and she was stunning.

I always thought I was the only 30 year old with a nice Fedora collecton...apparently I was wrong.

Brian -

You gotta have a cool 'Pork Pie' hat (any color) as part of your collection!

They're one of my favorite lids!

Those are super cool!! If I remember correctly Charlie Parker as well as Frank Lloyd Wright (so close and yet so far huh?...talk about different walks of life although both were "out there" artists in their respective fields) wore them.

Bird and Frank were copied by all the others. Bird died young, after having lived through a lot of sadness. Porkpies were cool--- especially those worn by Sinatra. I am a great fan of Art Tatum (listening to him right now), Mongo Santamaria, Cal Tjader, Dave Brubeck, Ray Baretto, Count Basie, Nat Cole, Fats Waller and dozens of others....may of whom looked great in Porkpies. Those days are gone, but not from my memory. But I digress....we were talking about 1915cc engines, IIRC.

Exactly - how COOL would it be to be throwing out major vibes wearing a Pork Pie hat while crashing through the gears winding out your 1915?!

Pretty cool, I'd say!

I nominate the Porkpie Hat as the unofficial 'Official Hat' of the SOC. That's the epitome of 50s cool. ... I'll be looking at the Goodwill Store for mine. This link has a Porkpie and a fedora:

http://www.villagehatshop.com/b2b-jaxon_porkpie.html

($180 for a hat is a little rich for my blood until I'm done with the car.)

I second the nomination!

Well Cory; the $180.00 price is for a dozen of them. A single one would cost $32.00. It'd be a good idea to order them in bulk and offer them at a significantly discounted price to SOC members....

$32 dollars leaves enough remainder from $180 for me to purchase some English lessons -- so I can learn to read, eh?
I'm a dumbass, but I'm STILL voting for that as the official hat! And now it looks like a bunch of us can go in on a bulk order -- thanks to Ricardo's ability to read fine print!
WOO-HOO!

Actually; by buying them in bulk each one would be $15.00 so you're $165.00 ahead....

i just threw up in my mouth a little.....

Yeah, maybe. But YOU have a roof! I already said I'm a dummy -- but I don't have to be a wet one! Water runs right down the front of my dunce cap and gets in my eyes. Have a heart!