how fast should my 914 be?

[robphelan]

Hi everyone, I just bought a 1974 2.0L 914 with dual 44IDF webers on it. I just had them rebuilt and had the engine tuned up.

The previous owner made some major modifications to the car (larger intake & exhaust, new valve guides, European pistons and cylinders, counterweighted crank & balance, Casey Hunter headers among other mods..) and I'm worried that it is not as fast as it should be.

I've topped out on the highway at about 92 mph. Does anyone have any suggestions? I know I need to have the carbs synchronized, but would that make such a drastic difference? thanks a bunch.

rob.
robphelan@cyberdude.com

[bowlsby]

The specs say the top speed is 115mph, but I've never had mine above highway speeds.

I'm sure there are some racers who can tell us what its capable of...they do have a 150mph speedo but I thought that was more of a dream than reality...8^)

[URL=http://www.pelicanparts.com/914/technical_specs/914_performance_specs.htm]


[This message has been edited by bowlsby (edited 07-23-2001).]

[Dave at Pelican Parts]

The 150 MPH speedo is mostly for laughs. Most mechanical Porsche speedos (like our 914s) seem to read high, at least at the higher speeds. I've had my car up to 120 MPH indicated. I think it might have had another 5 MPH in it, but I would have needed another 20 miles to get there...

My engine is stock, with FI. It was turning about 5000 RPM, I think (it was a while ago, so I'm not sure on that), in 5th gear.

What kind of RPMs were you reading when you were at 92 MPH?

--DD

[mejulihn]

Since your car has significant mods, there is a good chance it is not running on stock-sized tires that came on the car (165SR/15). Tire diameter makes a lot of difference if the speedo has not also been recalibrated. If you really want to know how fast you can go, get a willing rider (so you can keep two hands on the wheel) and use a hand-held GPS to measure your MPH (or KPH if you prefer).

[robphelan]

Well, the previous owner put the old Mahle rims and tires back on before he sold it to me. I figured this out because the rotors are drilled for 5-lug nuts. It does have 165/15 on it currently.

As for RPM at top speed - i'm not sure. I'll have to check and get back to you guys.

Also, another observation... i'm cruising along just fine, accelerating all the time, until I switch from 4th to 5th gear. It feels a lot more like just a cruising gear. I really can't accelerate at all in 5th gear. Is this normal? thanks.

[bowlsby]

Please don't get the wrong idea...we are not encouraging you or anyone to go test the top speed of your car, just to find out...just curious if other experienced drivers under safe conditions, and likely on the track, can report their top speeds....

<>

[campbellcj]

It's also possible that you have very short gears.

FWIW I've had my 73 2.0 up to 130mph indicated, which is obviously way optimistic but it was clearly well over 100mph. We were flying...it was in the desert on a LONG straight downgrade.


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Chris C.
73 914 2.0
70 911E Targa
campbell.chris@gte.net

[B Komar]

I have had my car up to around 128MPH on a desolate 2 lane that you could see for miles. That run started with a downhill slope. I was turning around 5400RPM in 5th (with my old [bus] 2.0 with a progressive holley). Two weekends ago I managed a top speed of about 102 on the straight (2800ft) at Heartland Park Topeka, before I had to slow down. That was in 4th at redline. I never found the need for 5th on that track. I was the slowest car there. I think that 115-125 on a LONG, LONG straight should be in the ballpark. Brian

[John Rogers]

I've had my race 914 to 7500 RPM in 5th gear and it was really light in the rear with no down force back there. I have no idea how fast that was but I was passing a 914-6 in a vintage race and he was going like hell. I have also had our 1987 Turbo over 160 MPH and it was as stable as I wanted it to be. I would guess a warmed up 914 should do 120 or so. You can download the GEARS.EXE program from here on the PP site and do some measurements to get a pretty close idea of the real speeds vs RPMs. Good luck.

[Dave Bell]

My underpowered 1.8L with cat converter will easily do 92 mph. You should be able to also.

To eliminate wheel, gearing and speedo uncertainties, borrow someone's handheld GPS, find a straight stretch of traffic free road, and let 'er rip.

The GPS will give you true land speed, and as a bonus you will be able to calibrate your speedo. Might make your job easier to bring along a passenger to jot down the info... unless you don't want their weight to slow you down.

My car with undersized 195/55/15 tires read 100mph when it was actually going 89mph... a little over half of the error was due to tire size and the other half of the error was due to an optimistic speedo.

- Dave

[Kevin@ojai.net]

92MPH sounds pretty slow for the max speed of a 2.0 914. My Superbeetle mechanically could go faster then that (had a bet with a friend), but was really scary. I have never really tested the top speed of my 1.7 914, but when In San Diego a while back I was going appx 100 just fine, It felt like it still had allot more to give.

But with these 30 year old Aircooled cars of ours, I don't think going much over 75 for any amount of time is wise. Actually I think that could be pushing it -- depending on the climate (not to mention the risk of the CHP, and the Idiot ahead of you only going 55 in the 1988 Ford Escort)

-Kevin

[Bleyseng]

It sounds like the carbs need adjustment because you should be able to hit 115-120 mph on the speedo. Or maybe not enough fuel to the carbs?? low fuel pressure or a bad filter??
I have hit 120mph easy on the I-90 bridge with my 914. I am running 205x50x15's so that's about 110mph.
Geoff [img]http://www.pelicanparts.com/support/smileys/nono.gif[/img

[prattrc]

I hit 105 on the speedo in my old Euro 72 1.7 with dual dellortos and monza exhaust. I was on a long, flat, high-walled bridge over a swamp in central Florida at 5:30AM.

I had to slow down 'casue I came to the end of the bridge and FHP are not very nice to little orange Porsches going 35 over the limit.

But I wasn't at red in 5th, I think it had a little more to give.

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Ray
73 914 2.0L

[John Rogers]

This may be a silly question, but are both carbs opening fully (not 3/4 or over full) when the throttle pedal hits the stop in the floor board? When we installed the new engine in my race car I set the limit to 3/4 open to keep me slowed down for a few hours of run time.

[roadtrp204]

According to the Porsche tech book for the 914 up to 74 the stock gear ratios are as follows:
1st 3.091:1
2nd 1.889:1
3rd 1.261:1
4th 0.926:1
5th 0.710:1
r&p 4.429:1

This would indicate the both 4th and 5th are overdrive gears. I threw the numbers into a gear calculation program with 205/60/15 (26") tires and a red line of 5800 rpm.

The results for top speed at redline in each gear are as follows:
1st 31
2nd 50
3rd 76
4th 103
5th 135.45 mph

I think most stock 914s would be hard pressed to be able to pull redline in 5th, so 115 to 120 would sound about right.


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Chris
75 914 2.0L

[This message has been edited by roadtrp204 (edited 07-24-2001).]

[sammyg2]

Pretty sure I could pull redline in 5th, but my redline is probably closer to 5500.
I had a bone stock (except for exhaust) 71 914 with a 1.7liter many, many years ago and I had it up to an indicated 120 with stock sized tires. I have no idea if that was accurate, but it felt like 200 mph.
The car had less that 60,000 original miles on it at the time and ran like a top.

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Gerald Gore II (Sam)
73 914 350 small block

[harekiller]

My 1.7 comes out of 4th at 90mph, with a little down hill I get around 115, I can cruse at 100 or so easy.

[Kevin@ojai.net]

You mean sustained speeds of 100 (over 15min.) I have driven my '72 1.7 Up the 5 to Chico (from Ventura) and down to SD a few times, and I always feel like much above 75 for sustained times is really pushing it.

Revving an air-cooled engine over 4K for a long times seams like asking for trouble. But I guess after melting pistons on 2 diff close to stock bug engines at speeds of around 70-75 makes me a little cautious(Yea I know my foot weighs a little too much). I know these T4s of ours are tougher then the T1s, but how much so? I know I do rev my 1.7 up pretty high sometimes, but never for more then 5 min or so (windy parts of roads can be allot more fun if you keep the car in 3rd Lets you pull out of the turns faster, and slow down with out using the break as much)


-Kevin

[This message has been edited by Kevin@ojai.net (edited 07-24-2001).]

[Roland Kunz]

Hello

The stock average and used 100 HP euro engine will rev to the redline on the straight higway. Some even go higher. Partially becourse the tires do have different dynamic rolldiameter.

The 2,0 will pull straight trough up to 5000/min and then gets slight asmathic.
At 5500/min the engine is asmathic and beyound is possible.

But I also had engines that pulled up to redline without any fuss. A fresh rebuild ( say blueprint ) engine broken in and with harder valve coils pulled up to 6000 in one ease and then the powerdrop came on. The same engine with 40 Solex reved to 6500 redline and would have pushed bejond that.
Stock FI cam, stock Valves, Alfa Romeo 33QV Aircleaner
44´s sound a bit to large also the other mods indicates a more rev orientatet layout.

44´s make only sense with a 2,4 on or a really rev orientatet made engine.

Anyhow the parts should pay back on the power curve.

I would start to look very close on ignition and carbs set up.

Grüsse

[SteveStromberg]

Your 914 should do at least a Ton. I agree with Roland you need to check your timing and carbs. Steve