Getting significantly more hp from a 1.7 liter 914?

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deathpunk
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Getting significantly more hp from a 1.7 liter 914?

Post by deathpunk » Fri May 11, 2007 8:57 am

Hi Guys
I've been looking at 914s lately, and am looking at a really nice 1970 tommorrow as well as a 73 2.0 sometime next week.

My Q is:
I know other posters have spoken of getting ~100 hp from 1.7 liters...but what if I went to a bigger p/c setup, raised compression a bit, ran a hotter cam, with dual webber or Dellorto carbs, header/exhaust? What can be done with a 1911cc motor?

Is the increased displacement worth it?

Additionally, if I end up with the 73 2.0, is it worth going to 96mm or just get mahle euro 94mm? I want something reasonable quick when all is said and done. Looking for 120+ crank hp.

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Bleyseng
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Post by Bleyseng » Sat May 12, 2007 1:30 pm

1.7l with djet & a 9550 with 96mm P&C's, 9 to 1CR, 42x36 valves will be 100hp

2.0L with djet & 9550 cam, 96mm P&C's,8to1CR, 'bout 115hp. Add a CFR header and you are at the 120hp.

Quick? small tires to 205x50's, switching the 3rd and 4th gears to M&S gears make a close ratio box and the 120hp make the 914 "quick".

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Piledriver
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Post by Piledriver » Mon May 14, 2007 4:12 am

You could probably build a 160++ HP NA 1.7, but it would cost a ton, and be undriveable on the street.

OTOH, a 1911@~120HP on Webers or perhaps with MS and the 2.0 manifolds etc and matching head work could be fun though, and possibly cheaper and more reliable-when-beaten-on than a 2.0 crank based motor.

(DJet is limited to very close to stock cam etc, works OK in that use)

If you were considering boost, the 1.7 head register get the win, seal better from most accounts.

(Don't need to do jack to the 1.7 crank and rods, they are near bullet proof as stock, 8K when properly balanced, assuming proper valvetrain etc)
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trscott
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How to get more power from a 1.7L?

Post by trscott » Sun Feb 24, 2008 11:16 pm

Well, to each his own, but my plan?

Send the core to Jake Raby and pick any one of his kits, depending on your taste; == Power, performance, street manors, longevity. He doesn't care what size it started life as, just that its a healthy clean core.

You could easily spend more time and money with add-ons and such, but he's already done all the research and you know what you're getting, and judging from the testimonials I've read, his stuff works as advertised, and he stands behind them. That's why I didn't worry whether I got a 1.7L or a 2.0L, if its a core for Jake, they're all the same.

In the meantime, I'm not going to spend a lot of money on this engine, just see if I can get it running with reasonable manors till we save the coin for Jake's kits.

Of course YMMV...

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raygreenwood
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Post by raygreenwood » Mon Feb 25, 2008 9:06 pm

You can get just at or just under 100 HP with a 1.7 at standard displacement. It is a lot of work. It takes a great cam, very good exhaust, higher than stock compression, great balance, 42 x 36 valves, some porting, killer ignition and a very good injection system.

I built one with a web # 73 years ago that with lots of heavy massaging and tweeks to D-jet got right at 102 HP on the dyno. It was a hot runner. and died of different causes other than heat at about 85K.

Also...you cannot run an engine like that with just any set of gears. It has to be optimum to keep it alive. Jake has better cams now than the #73....but its still safer to probably get that kind of output with a slightly larger displacement....rather than running close to the ragged edge.

If you can find a new set of original domed pistons...a lot can be done to by the very circumspect mechanic. Those were killer pistons and matched to the shape of the combustion chambers. As they were from the factory...they were not bad at all.Ray

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Rick_Eberle
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Post by Rick_Eberle » Thu Feb 28, 2008 8:15 am

I just put mine on the dyno today and got 76.8hp at the wheels...

http://www.youtube.com/v/M9zDgByXQSk

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raygreenwood
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Post by raygreenwood » Thu Feb 28, 2008 9:50 am

What were the engine specs? Compression, cam...which pistons...and what was deck?
76 hp...was almost exactly what a 1.7 with flat tops gets. The even lower compression set up....with dished pistons generally gets about 68 hp.
I have seen some dished get 70+ if a bit of deck was taken out .

In general...if its tuned ou tcorrectly and has proper deck and is set up to stock dimensions internally, the stock domed pistons generaly get right at the advertized 80+.

All of these #'s can be down if teh injection is not tuned out as well. Ray

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Rick_Eberle
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Post by Rick_Eberle » Thu Feb 28, 2008 4:53 pm

I found a stash of NOS domed 90mm piston & cylinder kits here in Australia.
Cam is a Web 86 (270Deg, 0.423" Lift), deck is 0.80mm, no head gasket, compression is 8.32:1.

Heads are stock 1.7's, stock valves, with the opening of the intake port opened up slightly to match the taper of the manifolds. 42mm ITB's with MegaSqirt II & EDIS.

More info here

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raygreenwood
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Post by raygreenwood » Thu Feb 28, 2008 6:15 pm

The deck s a little large. Not hideous...just a hair on the largeside. The stock deck measured at the piston edge was generally between .065-.079".
If you got rid of teh gasket and shim you should have around 8.4-8.5:1...depending on valve margin and what you did to the chambers.

The 1.7 with stock high compression is all about velocity. I would bet you are losing a smidge either due to the itbs and the 42's...and/or....the lift on the 86 cam is a little more than I would go for with that short stroke.
You should get better hp and torque with that set-up. Certainly not less than stock. Ray

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Rick_Eberle
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Post by Rick_Eberle » Thu Feb 28, 2008 9:01 pm

uhhh, Ray, that's 0.80mm - 0.031"... and the power was at the rear wheels, not at the flywheel.

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raygreenwood
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Post by raygreenwood » Fri Feb 29, 2008 9:23 am

:D Excellent!
Yeah...that little "mm" just slipped by me. The .031 is actually about as tight as you want to get. If you are getting 76.8 at the rear wheels....you are above the factory curve. Nice!

I still would bet that you can get more with smaller TB's.

the4ork
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Post by the4ork » Sat Apr 05, 2008 11:05 pm

what does a 1700 with dual webber itc carbs, and a vac advance electronic dist with msd coil put out? everything else is stock, might do a custom exhaust with maybe one resonator and a borla muffler

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raygreenwood
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Post by raygreenwood » Sun Apr 06, 2008 2:21 pm

If all else is the same...cams, valves, heads and if using 2tock fuel injection spec compression...it will put out slightly less than than it would wit hD-jet...most probably 76-78 plus. The stock fuel injection did great with what combination it had. Its cam profiles were specific to the injection...and barely adequate for that. Those same stock cam profiles were not excellent for carbs. Ray

Laptom
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Re: Getting significantly more hp from a 1.7 liter 914?

Post by Laptom » Sat Feb 15, 2014 3:39 pm

How flexible is the standard D-Jet?

Just bought a nice 1970 1.7. Want to paint it back to original green color and dropped the engine & transmission.
Just looked at the transmission and looks good (need new first gear & synchro, change gasket set and clutch). Want to start with the engine while the painter take a look at the body.
Not sure what to with it. Just ran a few miles with the 1.7, sound solid and fun.
So got a few options:
1. Low budget, just clean every thing, new bearings & gaskets, check wear&tear parts and replace if needed (cam, bearings).
2. Low budget, upgrade 96cc P/C, new cam, stage 1 heads, good exhaust. Stock crank, stock FI (D-Jet), stock ignition. So just a nice, balanced 1911.
3. Mid budget, upgrade crank, P/C, cam, heads, exhaust. What to do with the FI (Carb, MS, original D-Jet) - go for 2056 or 2270.
4. High budget, upgrade crank, P/C, cam, heads, exhaust, MS FI+Ignition (twin spark) - go for 2270 or bigger.


2. Sounds now most logic because I don't want to go to the MS or Carb route. It is a cheap upgrade with some fun in my believe. Is the D-Jet good enough for the 1911, and what needs to be changed on the D-Jet?

This will not be a daily driver. Just a fun car for the weekend summer cruise & fun.

Any help what is possible with the D-Jet is appriciated. Not scared for MS or other FI, but new to Aircooled engines and try to keep the first project easy.

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Piledriver
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Re: Getting significantly more hp from a 1.7 liter 914?

Post by Piledriver » Sun Feb 16, 2014 12:27 am

If the djet is working well, it will have no issues with the slightly larger motor with the stock cam, but it will need a few tweaks... Primarily fuel pressure cranked up to compensate, perhaps a ballast resistor in the head temp circuit., mps may need slight adjustment etc.

Having said that, it will be tricky going from 90mm bore to 96mm bore and keeping the cr and deck all happy with the stock or close enough cam... something will need done, and a web73 is about the limit of the djet tweakage.

a larger cam wants/needs the added compression, but will not play nice with djet.

For detailed tuning of djet there is excellent documentation online here:
http://members.rennlist.com/pbanders/

MSextra/MS3 and DJet really do not compare, with djet you are ~blindly tweaking knobs on a black box, on MS it's a fabulous datalogger (MS3 will do ~400Hz to the sdcard) that happens to inject fuel and fire plugs too.

I STRONGLY recommend replacing all the fuel lines, esp in the tunnel, they are vinyl and very brittle after 40 years.
I used brake line with unions at the shifter area to allow getting them in, occasisonally you can buy prefab SS ones.

The newer fuel line from Gates etc can tolerate alcohol in fuel etc, the "Good German woven cover EFI Line" some still recommend cannot and it tends to fail quickly. Do not go cheap here, but also do not hesitate to replace the fuel pump with a modern unit, and consider relocating it up front where it belongs.
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

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