Replacement Camshaft for a Fuel Injected Engine

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72_square
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Replacement Camshaft for a Fuel Injected Engine

Post by 72_square » Wed Apr 28, 2004 5:42 am

Building my new engine and I am stuck on the camshaft choice.

Engine spec:
Engine will be used in a type three square, that gets fully loaded quite often. Engine will be a daily, with low revs, nothing over 5000rpm. Don't want big power, just smoothness and reliability.
New case
1776cc B&P (90.5 with a 69mm crank)
Standard 040 heads with a three angle valve job, no porting.
Pretty much standard everything else.
Will be aiming for 7.5 compression i think (regular gas)
Will be using standard type three fuel injection set-up. I understand that this can cope quite happily with the 1776cc setup with a tweak in the fuel pressure.

I've been told that the stock cam is best, but I'm worried about the mexican/brazilian replacement cams. Should I stick with the stock or look at an aftermarket cam. How about the near stock webcam 86 or the scat C20?

If I start tweaking the cam, am I going to shag up the fuel injection settings too much? I want to keep it simple and not get into tweaking the MPS and other things.

Craig

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Post by MASSIVE TYPE IV » Wed Apr 28, 2004 8:40 am

The stock cam isn't even optimum for a stock engine. Nothing heats up heads like a stock cam!

Web cam makes several really good cams for an engine similar to this.

72_square
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Post by 72_square » Wed Apr 28, 2004 9:39 am

Jake

Thanks for that, I never thought of asking Webcam direct! I've sent them a fax, as a phone call from the UK will deplete my engine funds too much.

I've been debating the stock/aftermarket cam for a while. I'd rather go for a quality webcam and lifters that will do the job right.

Craig

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Post by MASSIVE TYPE IV » Wed Apr 28, 2004 9:44 am

Thats the only way to go..
I'd look into a Web 86, or 119 for that application.

72_square
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Post by 72_square » Wed Apr 28, 2004 10:12 am

Have you built or run something similar to this? My main worry is the fuel injection playing up with the different cam and increased displacement. I know I can tweak up the fuel pressure to solve the displacement issue, but will the mild cam confuse the rest of the FI system?

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Post by MASSIVE TYPE IV » Wed Apr 28, 2004 10:37 am

oh yeahh. Forgot it was FI....

hmmn, let me look at some files on that one.

Guest

Post by Guest » Thu Apr 29, 2004 12:33 pm

Allow me to chip in here.
The stock f.i. will handle the more cc with only minor mods.
As for cam change with the stock D-jet, I´d look at CB´s 2280 "cheater" cam. Or a stock T1 with 1,4 ratio rockers. The C20 is out. Maybe, a web 86. Bugpack 270 degree, maybe. That one is very mild, yet gives about 8-9 hp on a stock 1600 T1.
Bump the C/R to 8 - 1. Help the heads flow a little better, not much just a little.
Get Turbo Thomas to make you an exhaust, (when he´s done with mine :wink: )
He and I have the perfect header design for your engine, and car, which will give you that extra 8% torque over an off the shelf header. AND, it is almost not visible from the rear...
T.

72_square
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Post by 72_square » Fri Apr 30, 2004 3:07 am

Looks like the Bugback 270 is very similar to the web 86. I've put a technical question to bugpack on this one.

I was thinking of between 7.5 to 8 for compression. Remember I've got standard 040 heads and standard size valves with no porting. I thought the standard exhaust would be ok for this size engine. I'm not really increasing the airflow into the engine (slight cc increase), so I didn't see the need to go too mad increasing the airflow out of the engine.

I'm going to see what feedback I get on here and also from the cam manufacturers. if someone can definately say 'I've built the same engine with this cam and it ran sweet as a nut', then I'll be happy. I'm putting a lot of hard cash into this engine and building it myself (machining & balancing by shop), I also need the engine for the summer. hence the cam must be right first time around. If there's any doubts I'll have to stick with the stock one, can't afford to experiment!

Guest

Post by Guest » Wed May 05, 2004 9:46 am

I've been looking closely at the CB Performance cheater cam, as suggested. This is the only cam I've seen that says 'fuel injection' in the blurb. Anyway, these are the figures that I've dug up

Stock cam:
Duration @ 0.05 = 224.5deg inlet, 228.5deg exhaust
lift at cam = 0.291, lift with 1.1:1 = 0.316
lobe centres = 107.6deg

CB Cheater cam
Duration @ 0.05 = 222
Lift at cam = 0.359, lift with 1.1:1 = 0.394
Lobe centres = 107deg

I think the following is true, but please correct if required:
More lift will allow more fuel to enter the chamber, thus increasing horsepower without any effect on low rpm performance
If the duration is Increased it would sacrifice bottom end performance, cheater is slightly reduced: ok for bottom end torque
Lobe centre angle reduction will again give better low and mid range response.

If the above is true, then the cam sounds very well suited to my needs.

Questions that I would welcome your input on:
I assume that as duration is virtually identical to stock, I should keep the compression ratio at 7.5:1 as a max.
Will the higher lift give me poorer fuel economy? eg, more fuel gets in, thus petrol consumption increases?
Would you suggest heavy duty single springs with the higher lift?

72_square
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Post by 72_square » Wed May 05, 2004 9:49 am

That was me, not logged on, Doh!

Farmer out of town

Post by Farmer out of town » Wed May 05, 2004 5:52 pm

Yes, i would install a set of sgl. hd springs.
I would also bump the C/R to 8-1. Because of the more actual seat duration it is not a problem. (It is actually designed to run 8-1) I have done 8,2-1 on regular 92 RON gas. No problem. (Carbed tho)
I have not experienced loss in bottom end with this cam. Not even idle is affected with stock carb, as long as you stay above 820 rpm.
Especially with the more cc you intends to be running, you will get an engine that will pull pretty much like a stock 1600, only more, - with less head temps. You gain a little more rpm, about 400.
Fuel economy is a tad better than stock. It really likes a better exhaust.
T.

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raygreenwood
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Post by raygreenwood » Wed May 05, 2004 9:24 pm

Yes, 8.0:1 compression should be your target. A better than stock D-jet cam should have similar to stock intake valve timing, a little better lift and slightly longer duration. I think the duration for D-jet actually looks a little short on that cam. Since the D-jet already has injection timing issues, the added duration (as long as you don't get crazy) actually helps to scavenge in as much fuel as possible laying around in the ports. The lift looks akay. Lift is actually less important on the vacume signature of this system...than duration is. For example, the basic web #73 for D-jet on type 4, has .486 lift and .262 duration. Thats a 1.7 liter with a shorter 66mm stroke. Being the shorter stroke, having a little more duration helps feeding fuel. But, at 69mm, you are not far different. Ray

72_square
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Post by 72_square » Thu May 06, 2004 8:16 am

Maybe the web 86 would be a better choice then:

Lift = 0.358
Duration at 0.05 = 234
Lobes = 108

This will give me the increased lift, a little more duration for maximizing fuel inflow and lobe centres not too different from stock. I presume this cam would be happy at 8:1 compression. The power band of the engine will be moved slightly up the rpm range, but not greatly so, still giving me good low down torque.

Few more questions:
Am I best getting an adjustable cam gear and setting the inlet valve to open at 7.5deg BTDC, as stock? This will keep it the same for the FI brain. Or shall I just get a normal gear and place the cam in, letting the intake open at the cam setting (whatever that may be?)

I think the cam choice is finally getting there. This must be the most difficult thing to sort out on an engine build!!

nroush
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Post by nroush » Fri May 07, 2004 12:39 pm

Jake,

The following specs were found in either Bill Fisher's "How to Hotrod Volkswagens" or from the cam manufactures. (I hope this chart is readable)

Cam Lift Duration Lob Center IO IC EO EC Overlap

Stock .322/.310 .224.5/.228.5 107.6 4 32 41 1 5

Engle W-100 .383 .236 108 14 42 50 6 20

Web 86 .358 .234 108 9 45 45 9 18

CB Cheater .394 .222 107 34 60 68 26 60


Craig and I have been discussing cam issues for a 1776 engine which would keep the FI and would have some modest head porting/polishing. We understand that higher lift could increase the air/fuel charge amount which is a good thing if the heads have been cleaned up. But higher duration would move the torque curve up the RPM range which for us is not a good thing. I was reading in a March 1989 issue of "dune buggies and hot VWs" that excess overlap is bad for torque in the low RPM range. I think overlap is derived by adding the intake opening to the exhaust closing to get the total overlap in degrees. Is this correct? Bill Fishers seems to like early opening and closing of both valves (with relation to TDC) in stock VWs but thinks with cleaned heads and better (extractor type) exhaust it could handle later valve opening and closing with more overlap.

Would it be reasonable to believe the Web 86 could be used in our proposed 1776 as a mild performance upgrade with little loss at low RPMs? Have you heard any feedback from a Type 3 FI owner who used any of these non-stock cams? We are trying to maximize torque at the lower RPM levels and are not going for higher top speed.

Thanks,
Norman
68 Squareback

72_square
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Post by 72_square » Tue May 11, 2004 8:19 am

Just one more point about camshaft durations. Using the inlet/exhaust opening specs from the bentley manual

Type 1/3 = inlet 224.5degrees, exhaust = 228.5degrees (average = 227)
Type 4 = inlet 234 degrees, exhaust = 227degrees (average = 231)

Now am I right in saying these are the same as advertised durations of the aftermarket cams? (or am I confused and these are the duration at 0.05 figures, help!!)

Hence the webcam number 73 for the type 4 is 262degrees adv duration, this is a 13.5% increase in duration.

If I apply the same to the type 1/3 engine, that gives an adv duration of 257degrees adv duration. The web 86 or bugpack 4061-10 give 270 adv duration. A good figure??

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