What camshaft

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lmcchesney
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What camshaft

Post by lmcchesney » Mon Jan 05, 2004 6:30 pm

The project is a 914 engine converted to 96mm x 80mm stroke. Heads are ported with 48mm intake and 38mm exhaust. Pistons are 96mm hypereutectic. Compression ration will be 8.5-9.5. I want to adjust the 2.0L D-jet system for this combination. I despritely need suggestions/experience on what the max. cam can be used. I understand comprimise of idel smoothness, low end torque trade off. Plan is for autocross/time trails.

Thanks,
L. McChesney
lamcchesney@netzero.net

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Bleyseng
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Post by Bleyseng » Mon Jan 05, 2004 9:31 pm

Usually the Webcam 73 is about it as the idle vacuum on other cams is too weak so the MPS reads it wrong.

You are going to have to take the car to a dyno shop and adjust the MPS for the right Air/Fuel mix for idle-partload and WOT otherwise you will burn it up.
Not too hard to do, but read up on Brads Djet site
www.members.rennlist.com/pbanders

Geoff

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Post by MASSIVE TYPE IV » Mon Jan 05, 2004 9:56 pm

If the D Jet feeds it, and it lasts a year without frying, I'll send you a hundred bucks!

D Jet is SAFELY maxed at a 2056.

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Dave_Darling
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Post by Dave_Darling » Mon Jan 05, 2004 10:58 pm

2316cc? That may be more than the D-jet will cope with reasonably. Biggest D-jet 914 I have personally seen so far is a 2.2 liter, but I don't know any more details than that.

Definitely take it to a dyno with wideband O2 sensor. You really need to get all of the load/RPM conditions checked to make sure the mixture is reasonable. (Probably something right around 13-13.5:1 except at WOT, where you want 12-12.5:1 or thereabouts.) Spending the money on that is the only possible way you can collect that $100 from Jake... ;)

...And even that's not guaranteed... :(

--DD

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raygreenwood
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Post by raygreenwood » Tue Jan 06, 2004 2:28 am

About 2.2 just barely will be the max in stock trim for 2.0 914 adhjustment. It can be done...but the dyno won't help you until you make some mods. There was actually a factory setting to the length of the armature rod, that will allow a few more newtons of spring pressure..to allow better part throttle enrichment. You have to totally disassemble the MPS for that though. An easier way, is to use a pair of constant running frequency valve injectors bleeding fuel pressure to the return line up stream of the main pressure regulator. With a restrictor pill in the back of each one, they can be set to bleed about 1.5 psi each from the line. Set the pressure to run at 36 on the fixed regulator. The two valve runs constant....to bleed it to 33 psi normal. The cut-offs for the two frequency valves run sequenced off of either a pair of microswitches on the TB...or from vacume ports in any number of places. As the throttle opens wider...it cuts of each frequency valve in turn....bumping the fuel pressure by 1.5 psi across the board. Cheap and very precise.

But you will need to have better fuel volume and pressure cntrol . Use twin pumps. The pressure fluctuations must be kept to under 1.0 psi. I have never found D-jet to be undependable. I have also never found properly maintained D-jet to burn up engines....but2.3 liter is really pushing it. Jake may be right. Most importantly because no matter the combo....all existing stock runners, plenums and TB are too small for 2.3 liters. The metering problems caused by this alone will burn you up. Ray

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lmcchesney
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What Cam?

Post by lmcchesney » Tue Jan 06, 2004 9:10 am

Very helpful information.
Lets reduce the stroke to 78mm yielding a 2.258. An oxy sensor is placed in the 4:1 exhaust site for measurement of all cylinders. A/F mixture gauge placed under the dash for constant monitoring. Additionally, Vacuum gauge also piped to dash. Fuel pressure gauge tap on the fuel runner during dyno testing. Double fuel pumps to feed each runner. Increased size of the rales to 3/8" dia. yielding about double standard volume. Fine tune the MPS and potentiometers on the Temp. sensors. This allows for accurate measurement of resulting A/F mixture throughout the range. Still, to obtain optimal HP, stick with a Web cam 73, use a 86a or 91?
Jake, your concern of, "Burning Up!", is this a result of excessively lean mixture, inadequate exhaust valve size or timing? You must be speaking with direct experience. David, you previously spoke of working with someone doing a >2.0L makeup. Has this been completed? If so, What is the results? Ray, are you stating that we will need different injectors than the 2.0L? Or, do you place a resistor/potentiometer between the connector to the stock injectors to obtain a constant injection? We have previously spoke of using injectors of higher pound injector (Mercedes, 280ZX) but were concerned regarding idle flows. Please advise.
Thanks,
L. McChesney

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Bleyseng
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Post by Bleyseng » Tue Jan 06, 2004 12:35 pm

Hmm Ray, others (including BAnders)have stated that the injector system is sized to run upto a 2.4L.
On this engine, find a 037 MPS as they seem to have more room to adjust for a richer mix esp at WOT I have found.
Using a cam setup for carbs will result in you installing carbs. The Djet will have problems with the valve timing.

Geoff

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Dave_Darling
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Re: What Cam?

Post by Dave_Darling » Tue Jan 06, 2004 12:58 pm

lmcchesney wrote:Very helpful information.
Lets reduce the stroke to 78mm yielding a 2.258. An oxy sensor is placed in the 4:1 exhaust site for measurement of all cylinders. A/F mixture gauge placed under the dash for constant monitoring.
Wideband sensor, right? The narrowband one (the standard one you can get everywhere) is... Well, I won't say "totally useless for tuning", but it's not going to give you very good information. The NB sensors work very well at telling you if the mixture is right at stoich (stoichiometric, roughly 14.7:1), or richer or leaner. But they are very poor indeed for telling you how much richer or leaner. That reading is more dependant on the temperature of the sensor than the O2 content of the exhaust.

Aircooled VW engines like to run richer than stoich-it helps them live longer. So using the NB O2 is not going to provide the most useful info for you.

A wideband O2 sensor, however, can be very accurate in showing you just how rich or how lean the mixture is. But the sensors are expensive, and you need particular circuitry to drive them. That's more $$. But they are the only way, I feel, to get enough mixture info to tune the system.
Still, to obtain optimal HP, stick with a Web cam 73, use a 86a or 91?
D-jet will not tolerate the aggressive grinds like the 86a. The idle in particular will suck rocks. The 73 grind is doable under at least some circumstances, but some folks have been unable to get even that one to work to their satisfaction.
David, you previously spoke of working with someone doing a >2.0L makeup. Has this been completed? If so, What is the results?
I didn't work with him--he used to run autoXes and time trials locally. All I really know is that he bought the car with a 2.2 engine with D-jet on it. I don't know who did the work, nor what work was done on it. The car had run for at least a year by that point, but I haven't been running with that group in several years now. I don't know how well it held up.

There are others on the BBSes who have D-jet 2056cc engines, and they seem to work. I have not been involved with the buildup of those, however, nor with the tweaking to make them work. Do a search on your favorite 914-oriented boards and see what you can find.

--DD

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Bleyseng
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Post by Bleyseng » Tue Jan 06, 2004 2:37 pm

I am one who runs a 2056 motor for 4 years now. It took awhile to figure out the MPS settings and some dyno time to adjust it right.
My best dyno effort has been 95hp to the rear wheels which approx 115hp at the flywheel.

How much hp are you shooting for? For AXing or track use?

For AX the suspension mods are much more important than a high hp motor. I run with 1.7's, 2.0, and 2 2.3l motors. The 1.7 car kicks our butt most of the time due to its set up and driver. The 2 2.3L cars usually come in last place! Both run carbs and have fuel delivery problems on the tight courses and overpower the track other times as they need suspension mods.

Geoff

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lmcchesney
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Post by lmcchesney » Tue Jan 06, 2004 3:24 pm

Thanks Guys,
Dave, since I paid less than a $100.00 for the oxy sensor, it must be a Narrow Band. But do you need a broad band once the FI is set? I believe the Dyno. shop has a broad band oxy sensor for the tuning. Is it not reasonable to fine tune the setup on the dyno and then use a NB oxy sensor for monitoring? Is a CO sensor a better option? What about the addition of cylinder temp. as an additional input to prevent excessively lean mixture.
We presently have a WebCam 73. The rep. at WebCam stated the 86a was better for FI systems. Seems the 86a has a larger flank (opening closing ramps) for the FI system. Stock grind is Intake 234° and Exhaust 227°, with Exhaust overlapping the intake by 85°, with a lobe separation I believe of 145.5° (Intmx at 105° and Exhmx at 70.5°). That makes the lobe separation angle >>wide, if I did the calculations correct.
Does anyone know what Jake's cams are (i.e. RAT 225)? I'm just not smart enough to be able to correlate the cam grind to the limitations of the modifications possible with the D-jet system. Why do grinds like the 225, 91 etc, work with a carb. system which no feed back or adjustments but will not work with a continually monitoring and adjusting D-jet FI system?
Side topic, will a 2.0L D-jet system work with the 1.7L distributor. Are the ECUs different?

I agree Geoff. In some ways I want to maximize the HP to see what is possible. No specific value(130 vs 150 vs 175?). I too understand HP never makes a better driver.
Suspension changes are:
Full Stable Energies Chromoly roll cage, 19 mm torsion bars, bump steer, 22mm Weiltmeister sway bar, front struts look/function fine, new composite bushings, tie rods/joint looks good.
Rear: Koni gas adjustable, 180# springs, composite bushings. Brakes BMW 320i calipers up front with metal pads and 500°+ fluid, stock rears with metal pads, stock proportioning valve and steel braided lines/replaced liners and 17 or 19mm ATE master( not sure. was on car when bought and don't see a 17 or 19 on the top). Just finished 9 and 7" flares for 255 rears and 235 fronts. Have decided not to go with boxing the trailing arms or rear sway bar.
Would appreciate your thoughts.
Thanks,
L. McChesney

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Post by MASSIVE TYPE IV » Tue Jan 06, 2004 9:18 pm

I can see now that even though I almost hate the stock FI system, that I'm going to have to work on a combo that will make it work.

The cam is no as much of an issue to me as it is to some people. have ran a few cams with D jet that others said would'nt work, and it worked fine.

The stock systems are almost 30 years old- some are older. When troubleshooting ONE problem can take as much time as building an entire engine thats when say its time to throw it away.

The answer is CIS. Till anyone has experienced it on a TIV its impossible to explain. Guys keep the stock FI for driveability. Driveability is the definition of CIS in my opinion. AND it has HALF as many parts to leave you in the dirt on the side of the road. The ONLY car I have ever had leave me on the side of the road was a D jet 914. Since then I have had a huge prejudice against it.

Tear down engines that come from guys that have worked for a solid year OR MORE to try and perfect a combo- Just to have it melt a piston crown and you'll understand.

I know if I perfected a 2200cc combo for D jet that my 914 engine sales would almost double- but that liability is scary.

BTW my 225 cam is based from a stocker. The only thing thats stock about it is the lift. The duration is heavily split and lobe centers modified. The intake duration is even LOWER than stock. It works, and works well in stock - 2056 engine. Larger than that and I would not think about it.

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raygreenwood
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Post by raygreenwood » Tue Jan 06, 2004 10:12 pm

A Few things to think about. The cam in D-jet type 4 is the way it is for a couple reasons (1) The intake valve timing is set to be reasonably advantageous to the paired injection timing. Two injectors are reasonably close, two are not. Essentially, kind of like Kadrons, two cylinders are responsible for reasonable idle in the D-jet. This is why the D-jet appears to like to idle rich. It cleans up a little when running at higher rpm. This is also why later D-jet systems set to cleaner idle 02 settings ran better. If you can make it sequential in injection timing...it may help throttle response.
(2) The timing overlap is helpful to the vacume signature.

The importance of the web #73 is that it uses the earlier type 4 fuel injection cam timing. Its close to stock. The injection is timed from the distributor...which is timed from the cam.

A few notes on what is possible with the MPS. First, read Brad anders site. The volume of information is vital to understanding how this works.

One thing about using a scope or a wavetek meter for characterizing the MPS to the , is that it is still along factory lines of tuning. Factory tuning was rather crude in my opinion, compared to what the MPS is capable of if modified slightly. There are three adjustments inside. Instead of telling you about those, I'll tell you some of the mods I have made...and why.
By the way...dyno testing with D-jet is great, but is not a full substitute for driving and adjusting. A lot more can be done even after the dyno.

To really unerstand this next part, I would recommend finding an MPS that is really dead...and stripping it to the core to inspect and measure things. You will need a soldering iron.

One of the problems of the MPS in this systems is lean spots at part open throttle. The way this part works, is that at max vacume with throttle closed, the two vacume chambers in the middle of the unit, swell, pushing an iron core into the magnetic influence of the coil. As Brad has noted, the core can only go so far in and come so far out before it is outside of the parameters of the ECU to use the signal.

When the TB is opened...atmospheric rushes in...squeezes the cans...and lets the mainspring drive the rod out of the coil. Several problems with this can cause the part throttle leanness. (1) The leaf springs at each end of the core...that are used to keep the rod precisely centered. They have a tendency to arrest the enertia of the rod, and pull it slightly backward too fast. (2) part revacuming of the chamber at high rpm's.

The MPS also has a bit of the same problem with vacume as the vacume variable fuel pressure regulator in L-jet. Though both the diaphram in the fuel regulator, and the aneroid chambers in the MPS are both sensitive to middle ranges of vacume, the springs are not fully balanced linearly with that midrange vacume operation. They tend to be either in enrichment or not. It doesn't dally long in the middle.

First thing I did, was use a vacume pump and a bleeder valve and guage to establish at most maximum ranges of vacume, how far the the rod goes into the core at idle. Over about 17 hg ofvacume, the core did not move much farther in. Once establishing that...I put in an adjustable stop screw so it could not be drawn too far in at idle...and also so I have a "0" point for where it was supposed to be. Next....I ground a slot into the metal under the mainspring seat and added an external cover...so I could slip shims under the mainspring to adjust the mainspring pressure.
What does this do? Well, adding small amounts of pressure, allows the rod to dwell a little longer in the middle range position for part throttle enrichment...and increases the rate that the rod responds to the movement of the chambers. But...That drove the rod out of the set idle position in the core. How to correct? You need to look at a dissasembled core. It has a threaded aluminum core that makes up the pin end that pushes against the chambers....and that helps lower the mass andenertia...but at the core end, it has a washer/shim under the screw on spring seat. Removing that backs the rod up about .020". But...you have to add whatever you remove from the spring seat end...to the chamber end to keep the relationship the same. I used a handmade delrin cap.

Its worth it to note that I also removed the two leaf springs. This helped part throttle movement a lot. To keep the rod perfectly centered, I made a groove the length of the rod on the side, with a fine file. Three of them actually...120* apart. About .010" deep. I JB welded in..carefully...3 thin slivers of bondable etched teflon sheet. There is now about .0005" of clearance around the rod in he coil. Its smooth as glass and will not hang up. These are glides to repace the suspension of the leaf springs.

This level of tuning and the resulting adjustments in the 3 main adjustments to the back of the MPS allow a lot of finer adjustment to the MPS and the mid range fuel mixture.

Something that helps as well on these systems, is stabilizing the fuel pressure noted before...which really makes the MPS adjustments more accurate and sensitive. It was also disturbing how unbalanced the flow from even new injectors is. Like as much as 10-15% different on the 40 or so injectors I pressure and time tested.
One of the latest improvments, is a hydraulic bleed valve teed in right before each injector. They all go to the return line. Each injector has small individual fuel adjustments to balance their output to about 1-2%. Thats how I balance injectors.

Adding a variable ballast to the CHT, for very cold or very hot weather helps greatly in control. A neat way to do this is with three subminiature relays, each wired in,next to each other,or in individual depending upon if you set them all the same to be cumulative, or individually . Each has a potentiometer attached to one leg. From a rotary switch on the dash, you can dial in which relay you power to drop its particular resistor in line. The sub-miniature relays with clean terminals work great and give about 50-75 ohm jumps to the CHT, for each one.

There will still be peaks that need enrichment the system cannot deliver on some engines. The reason why a vacume variable fuel pressure regulator will not work well on D-jet is the same thing that causes the MPS to not be a perfect adjuster on its own. The best thing to do is take the variable fue pressure regulator concept out of the vacume loop..and make it electrical, so you can drop in precisely what psi riseyou want...at precisely when you want it. That why I set the initial at 34-35 psi and keep it cinstantly bled back with a pair of saab/volvo frequency valve injectors. They pop in sequnetially near the top 5th of the TB stroke from a pair of micro switches breaking their grounds.

Lastly, I made a mod that makes the injection sequential. It uses a new trigger plate and plugs right into the harness. It still uses the same cam ramp length, with two cams and four sets of contacts... and the same two injector channels. It simply plugs into the existing harness so I can swap back if the mod doesn't adjust out right. I already know it operates properly, I just havn't driven it yet to see what its benefit may be.

So yes, there is a lot that can be done with D-jet. A lot more than factory. Sorry for the length. Ray
Last edited by raygreenwood on Tue Jan 06, 2004 10:56 pm, edited 1 time in total.

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Post by MASSIVE TYPE IV » Tue Jan 06, 2004 11:17 pm

Ray,
lets work together on this. You know the system way better than I do. I'm sure the two of us could make a combo for those hardcore guys that cry when they see carbs.

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Post by regis101 » Wed Jan 07, 2004 12:46 am

Perhaps a combo that concentrates on low end torque. Short shifting is also fun. The web 73 with 108 centers has the intake opening at 4, closing at 40 and the exhaust opening at 40 and closing at 4. This is at .050 lifter rise. Very little overlap. The FI cams that I have researched, are all using 8-10 degrees of overlap, again, at .050 lifter rise. It seems that stock FI, both D and L, are designed best for low rpm use, IMHO. Lets see an engine built within easy parameters. Stump pulling GRUNT. Just some thoughts

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raygreenwood
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Post by raygreenwood » Wed Jan 07, 2004 12:54 am

OK. The camshaft and engine combos you should be able to really optimize. Probably the first thing to really do (if you have not already done it) is to get a basic stocker of an old core set up so at some point you can see just how far a full bone stock engine with a bone stock system can go. From there you can see what its basic requirements and vacume issues are.

The sequential part can alleviate the cam timing issues, but not the need for some overlap that makes the MPS operable.

At some point finding away to add larger diameter runer pipes onto stock end stubs may help to keep manifold ratios correct (if you go over certain sizes in displacement). I already have an interesting way to increase the stock plenum size with very few changes...using stock parts...an a few others pieces.

I know a lot of your 914 customers want to keep the system basically stock, but get some more HP..and keep runability. Adjustment of stock FI, compression, cam, heads, stabilizing of fuel pressure etc....and a bad a*s ignition can do a lot. If you have a body for a mallory...even a bad one with a shaft in it, I can set up a plate and cams that can drop into the mallory body...for either stock of sequential.

The problem I see will be quality parts for the system. I already have new copper diaphram molds for the MPS made. I have one plate running in a friends type 3....he doesn't know that though....well maybe he does now. Those are no problem. Good FI harnesses are not hard to build when needed. I have the tools....a few sources for the connectors...and a mold to cast silicone around the wiring....that could be extended for a 914. Anyway...lots of things working and workable. Contact me on pm..I'll drop you a line as well. My next 2 months will be crazy. New job! Making solar cells with a semi-conductor manufacturer. Ray

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