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Discussion Starter #1
Back in March of this year, I did a partial rebuild of the engine in the '88 Spider that included 10:1 (nominal) Motronic pistons and liners generously donated by Ed Prytherch (alfaparticle) and a set of better cams from Richard Jemison. With the higher compression pistons and the bigger cams, I have been curious about the AFR curve in this engine given the often discussed fuel limitations of stock L-Jet. This weekend, Ken Vaughn and I hooked up the Zeitronix to log some data. A representative curve from one of the test runs is shown below. I am encouraged to find that L-Jet does a very good job of keeping the AFR close to 13:1 throughout the rev range at wide open throttle. Richard told me L-Jet could handle the 776/195 cam pairing without issues but I did not expect the AFR to be this close to the ideal, low 13s at the top of the rev range. Perhaps this information can be useful to someone considering engine improvements to an L-Jet Spider.
 

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Impressive! You have a good recipe for a simple and effective S3 improvement. Maybe one day you will get it on a dyno.
 

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Do you think the L-Jetronic would handle better cams with stock pistons equally well?

My wife's '76 Super Beetle has L-Jetronic FI; I'm continually impressed with the performance and reliability.
 

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Do you think the L-Jetronic would handle better cams with stock pistons equally well?
By better cams do you mean "better" than the ones that Rich installed or are you asking about those same cams with stock pistons?
If it is the latter then the answer is yes. Compression ratio has little effect on fuel demand.
It is harder to say whether L-Jet can handle cams that improve the volumetric efficiency more than these. If you could monitor the on/off cycle of the injectors at WOT and high rpm then you would see how much head room you have. Maybe a laptop based data logger and an interface circuit is available that would work. Or maybe one of the unused inputs to the Zeitronix ZT-2 could be utilized.
 

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Discussion Starter #6
I can't add much to Ed's answer. I have no doubt these cams or similar would would work fine in an engine with stock 9:1 pistons. The Motronic pistons helped by themselves but the cams changed the character of the engine, as might be expected.
 

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Richard Jemison
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Cams

Do you think the L-Jetronic would handle better cams with stock pistons equally well?

This info below is from an enquiry I sent today. Notice the suggested cams for L-jet are smaller, as I have to assume they are going in a stock head and there isn`t the mechanical expertise, or desire, to make simple pressure changes that allow the stock system to fuel larger cams. Cam lobe design is the critical event that prevents the limited fueling from going out the exhaust. Commonly this size pairing is OK for Motronic applications.

There are specific pairings for factory Bosh L-Jet, for Motronic versions, and and a couple of versions for stock compression 9.0 and 10.0(motronic piston) engines.
Using the smaller cams that work with the limited fueling of the stock FI units will work with MegaSquirt, but with the programmable of MegaSquirt, you won`t get the full benefit of the system
Attached is the PDF file of the various pairings that will fit in an un-modified head.:

These smaller cams are made on order as I only stock the Racing cams. Takes about 2-3 weeks for custom builds and delivery.

(intake/exh)
L-jet- RjR570/RjR1032 (pg 13
Motronic RjR45/Rjr1032 (pg 2 & 13) or (RjR195/1032)
MegaSquirt- RjR 429/RjR776 (pg 3 & 2)
 

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Alfaparticle, any plans to put your 1988 Spider on the Dyno so we can all see the difference from stock?

I have a stock 1988 Spider which I purchased in August. I plan to do a dyno run next week to see where I am and would be happy to share with everyone if there is an interest.

Also, I posted a plea in the Restoration forum for photos of the seat belts (lap belts) in a 1988 Spider as my car does not have them and I need to see what they are suppose to look like.

Thank you for your help.
 

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Rich Hanning - 65Sprint is the guy with the 88 Spider. Mine is a 79 with Webers and I posted dyno charts for it.
 

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65Sprint,

any plans to put your 1988 Spider on the Dyno so we can all see the difference from stock?

I have a stock 1988 Spider which I purchased in August. I plan to do a dyno run next week to see where I am and would be happy to share with everyone if there is an interest.

Also, I posted a plea in the Restoration forum for photos of the seat belts (lap belts) in a 1988 Spider as my car does not have them and I need to see what they are suppose to look like.

Thank you for your help.

PS: Alfaparticle, whoops, sorry for my mistake and yes, your dyno graphs very much appreciated!
 

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Also, I posted a plea in the Restoration forum for photos of the seat belts (lap belts) in a 1988 Spider as my car does not have them and I need to see what they are suppose to look like.

Thank you for your help.
I missed your post in that topic. I'll take some photos of my '88 for you.
 

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Cool thread, I missed it first time around. I just got my 86 back from having it's engine rebuilt with motronic pistons. Other discussions on 'what cams will work' have always led to 'none, you have L-Jet and that sucks' type threads, so I'm encouraged that you found someone to make you some cams (original poster of this thread).

655 Sprint, did you retain your VVT functions with the new cams?

Thanks,
John
 

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Discussion Starter #14
john802, no, there are no immediate plans to dyno the '88. I don't know but have heard 100hp at the rear wheels would be a reasonable number for a stock L-Jet Spider. This car had the automatic seat belt option too. I cut the standard mounts off of an '82 shell and welded them to the '88. Also had to relocated the motronic ignition ECU. I may be able to supplement Shakey's pictures. I'll look.

John533i, yes, the vvt was retained. I bought a 55mm wrench from McMaster-Carr to loosen the big nut. Cost for a new vvt cam was the same as the exhaust. I originally planned to ditch the vvt but Richard Jemison advised keeping it to maintain a reasonable idle. As it is, the idle is not as civilized as a stock L-Jet. I don't find it objectionable but it is a bit lumpy. I use the mechanical vvt on this engine.
 

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I don't know but have heard 100hp at the rear wheels would be a reasonable number for a stock L-Jet Spider
I think that 95 would be good on an honest dyno.
 

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Richard Jemison
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Idle

I originally planned to ditch the vvt but Richard Jemison advised keeping it to maintain a reasonable idle. As it is, the idle is not as civilized as a stock L-Jet. I don't find it objectionable but it is a bit lumpy. I use the mechanical vvt on this engine.
Retard the intake 1 notch on the VVT sprocket. Should calm things idle wise. Might improve 35-6500 rpm power as well.

Did you modify the weight in the VVT to raise the advance RPM?
 

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Discussion Starter #17
Thanks, Richard. I will give it a try. And no, I have not done anything to the VVT advance weights. I plead ignorance on that topic. Is the process described in your thread? I'll eventually report back. In the middle of prepping another Spider for paint.
 

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Discussion Starter #18
I needed to check notes before replying to Richard's LC suggestion above. I tried each of the combinations of cam lobe centers between 101 and 107 degrees. The idle is the best at 107/107. I ended up at 101/107 for the best compromise between idle and power characteristics.
 

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I ended up at 101/107 for the best compromise between idle and power characteristics.
That is where I landed when I experimented with timing race cams. Lack of piston to valve clearance prevented me from advancing the intake cam beyond 101.

EDIT: Rich, I probably told you this already that Jim Steck advised me to set the exhaust cam timing first and then do the intake cam. There is less interaction between them when you do them in that order.
 

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Richard,
I am slowly assembling a kinda hot 2L. Moronic pistons (Steck) at 10.5+ with an old head mill job (and some other work) with light carrillo rods, 45 DCOE9's, Alum. flywheel, CR gears, 4.3 LSD, and I want your cams (we'll discuss which after I get all the other stuff together).

I noticed some discussion on the vvt's. Is there any benefit (like better idle or low end), or value in a slightly hotter cam that can be tamed with vvt? I'd expect the easiest would be a mechanical vvt but other is always possible.

Thanks as always for all your freely offered expertise. My only contribution is an infamous "first-gear fix" and some GTA trophies from the 60's.

Robert
 
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