Yep, the retarded timing will almost surely cause higher temps...and very poor acceleration, unless you have really high compression in the first place. 32-36 BTDC tops. D-jet especially runs better in the upper end. You might also be sure to bend the tang on the inside of the vacume can mount if you are using the vacume retard and advance unit...to not allow the retard to drag the timing down below about 10 degrees at idle. It will get rid of a flat spot you probably did not know you had.
Turning the distributor counter clockwise is adavance, clockwise is retard.
What distributor are you using (last letter code will suffice) and what cam are you using? Stock...or web #73. If you are using the stock cam....slotting the screws on the breaker plate that holds the FI triggers and moving about 3-5 degrees max in the clockwise (advance) direction, helps to get a little more of the atomized fuel into the combustion chamber while it is still atomized..and may help valve cooling. On the web #73...this helps as well. Since it changes the vacume signature a little...the MPS...also changes the injection duration. You can watch to see if you have moved the breaker plate too far by tuning it at idle while a fuel pressure guage is attached to the ring main. When going too far in adavancing the FI triggers...the fuel guage will fluctuate in 3 psi encrements ...like a vacume guage...because the injectors are being held open for longer...dropping fuel pressure. If it runs best at an semi un-smooth guage position...you may run rich...if so drop fuel pressure by 2 psi. Ensure that fuel pressure is not dropping by more than one PSI when opening the throttle...or else it will run you hot. This is a common problem and is a weakness of older stock fuel pressure regs. Ray
Alternative (better cooling) Fan for 914?
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ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
Alternative (better cooling) Fan for 914?
I have extensively tested each cooling system with and without fan belts...changes of 9-16HP are evident with each engine and the 911 fan..
a better cooling system is not the answer, a better cooling engine is. By this I mean that we can make larger than stock, high CR engines run as cool as stock, a bigger fan is not the answer, and it may lead to other problems too. It all in the combo!
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Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
a better cooling system is not the answer, a better cooling engine is. By this I mean that we can make larger than stock, high CR engines run as cool as stock, a bigger fan is not the answer, and it may lead to other problems too. It all in the combo!
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Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
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maf 914
- Posts: 294
- Joined: Thu Aug 09, 2001 12:01 am
Alternative (better cooling) Fan for 914?
Jake,
Have you or Shad run your engine analyzer program using your 2270 set up with 96 Berils? Can you run more compression with the Berils? Or do you need to actually build and run one for baseline info?
Thanks,
Mike
Have you or Shad run your engine analyzer program using your 2270 set up with 96 Berils? Can you run more compression with the Berils? Or do you need to actually build and run one for baseline info?
Thanks,
Mike
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914Racer
- Posts: 56
- Joined: Fri Jun 07, 2002 12:01 am
Alternative (better cooling) Fan for 914?
Thanks everyone for all the input. Right now I'm trying to get my mixture sorted out. It's rich at idle and part load but goes lean at full load adding to my temp woes.
I'm pretty much stuck at 2.0 liters and with Djet based on my class.
Thanks again. This forum is BY FAR the best of all the ones out there.
-Greg
I'm pretty much stuck at 2.0 liters and with Djet based on my class.
Thanks again. This forum is BY FAR the best of all the ones out there.
-Greg
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Dave_Darling
- Posts: 2534
- Joined: Thu Apr 27, 2000 12:01 am
Alternative (better cooling) Fan for 914?
You may be sick of hearing me say this, but for your D-jet info needs, see:
http://www.914fan.net/djet.html
and for a detailed explanation of a whole lot of the D-jet parts, see:
http://members.rennlist.com/pbanders
Might not be a bad thing to invest in a rising-rate fuel pressure regulator. Or perhaps adjust your manifold pressure sensor.
--DD
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1974 VW-Porsche 914 2.0 (Type IV powered!)
Pelican Parts' 914 Tech Geek http://www.pelicanparts.com
http://www.914fan.net/djet.html
and for a detailed explanation of a whole lot of the D-jet parts, see:
http://members.rennlist.com/pbanders
Might not be a bad thing to invest in a rising-rate fuel pressure regulator. Or perhaps adjust your manifold pressure sensor.
--DD
------------------
1974 VW-Porsche 914 2.0 (Type IV powered!)
Pelican Parts' 914 Tech Geek http://www.pelicanparts.com
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914Racer
- Posts: 56
- Joined: Fri Jun 07, 2002 12:01 am
Alternative (better cooling) Fan for 914?
Thanks Dave! Right now we're tweaking our MPS. Without Brad's site and personal guidance we would've been completely lost.
Thing is, in order to get it rich enough at full load we have to run it so rich at idle that it barely runs and fouls plugs. I won't bore you with how we tested or replaced and tested again every last component in our FI and cranked up our fuel pressure but our O2 sensor and plug reading is still telling us we're lean at full load.
All we have done is bumped the compression a bit with Euro pistons and no head gaskets.
We're close, but very frustrated. We never would've gotten this far without help from the forum. Thanks again!!
We're off to Thunderhill!
-Greg
Thing is, in order to get it rich enough at full load we have to run it so rich at idle that it barely runs and fouls plugs. I won't bore you with how we tested or replaced and tested again every last component in our FI and cranked up our fuel pressure but our O2 sensor and plug reading is still telling us we're lean at full load.
All we have done is bumped the compression a bit with Euro pistons and no head gaskets.
We're close, but very frustrated. We never would've gotten this far without help from the forum. Thanks again!!
We're off to Thunderhill!
-Greg
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Racer Chris
- Posts: 665
- Joined: Sun Jan 13, 2002 12:01 am
Alternative (better cooling) Fan for 914?
Greg,
Have you added a variable resistor to the head temp sensor for the FI? If you wire it into the cockpit you can make adjustments while you drive to see if that will enrich your mixture where you need it. My experience shows that adding about 300 ohms is necessary in that circuit. Also by adjusting the MPS you should be able to correct the A/F ratio curve.
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Chris F.
www.tangerineracing.com
Have you added a variable resistor to the head temp sensor for the FI? If you wire it into the cockpit you can make adjustments while you drive to see if that will enrich your mixture where you need it. My experience shows that adding about 300 ohms is necessary in that circuit. Also by adjusting the MPS you should be able to correct the A/F ratio curve.
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Chris F.
www.tangerineracing.com
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HotRod
- Posts: 118
- Joined: Tue Nov 06, 2001 12:01 am
Alternative (better cooling) Fan for 914?
Jake, he may be limited by the rules as to what size of engine he can use. I'm limited to 1.8 litre in the SCCA class that I run in.
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
Alternative (better cooling) Fan for 914?
it is not about engine size, it all about the combo...
Someone above asked if I run the 2270 through my engine analyzer, yes 200 combos of it so far with 60 cam profiles, 25 CR changes, and 12 valve margin swaps, carbs,EFI and Turbo......The combos I have found best have been within 3% of the analyzed data after sea level corrections and atmospheric changes from the dyno.
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Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
Someone above asked if I run the 2270 through my engine analyzer, yes 200 combos of it so far with 60 cam profiles, 25 CR changes, and 12 valve margin swaps, carbs,EFI and Turbo......The combos I have found best have been within 3% of the analyzed data after sea level corrections and atmospheric changes from the dyno.
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Jake Raby
Raby's Aircooled Technology
www.aircooledtechnology.com
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ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
Alternative (better cooling) Fan for 914?
Greg...some thoughts on your MPS. If you can get your baseline adjustments set up so that at idle, off idle and part load...your are at least getting close together tail pipe readings...and it sounds like you have, then you have accomplished the most difficult part. The most usuual problem is one of two directions.
(1) a lean idle with a bump of fuel off idle, a rich or normal part throttle, back to a lean WOT. This is usually signifying that fuel pressure is correct or close to it...but overall spring tension of the center mixture screw is too light. It reacts too hard to the vacume ranges it needs to parrallel.
(2)a rich idle, a rich part throttle...and then lean at WOT...which generaly means one of two things. (A) the fuel pressure is approx. correct, the plate and chamber spring tension set from the center screw is approximately correct...BUT...the outer stop setting is too tight, not allowing enough stroke of the copper plate outward...to unload the stack...and move the rod in the armature. The outer cover plug...which is the outer stop, can only be adjusted at idle when the diaphram has been vacumed in. A good base setting to adjust from is to lightly contact the copper plate with the plug and start at 1/2 turn outward. Adjust and drive and check CO at WOT and move the outer stop about 1/4-1/5 turn at a time. Usually any adjustments of the outer stop equalling over 1.5 turns will leave you with a very rich flat spot off the line. (B) same situation as above...but if the outer stop requires having over 1.5 turns...then what is probably actually out of adjustment is the inner stop. That is the surrounding ring screw that the center main screw is screwed into. It contacts the keyhole intyermediate plate within. Between the outer stop screw and the inner stop screw...they dictate the total stroke ...and enrichment available to the copper load plate...with me ? So if you are having to adjust the outer stop screw more than 1.5 turns...it would be better to move the inner stop screw 1/4-1/2 turn out...to allow the whole plate assembly to vacume farther in...increasing the stroke...and allowing less adjustment to the outer stop. This will also entail about a 1/2 turn adjustment to your center load mixture screw to keep you around your baseline setting.
The object here is to getthe entire range of vacume reaction...idle...off idle..part throttle...wot...to be in one of two situations.
IDEAL: uniformly slightly rich or lean through all four phases. This would mean that a simple drop or rise in in fuel pressure of 1 0r 2 psi...or a 100 or so ohms more or less of CHT ballast would put you spot on.
You might find you like the ballast idea. If you use a variable potentiometer. You could give a very quick tweek right before you drive it to match changes in ambient temp.
NEARLY IDEAL: This actually might run quite a bit better depending upon th engine. Same as above...either uniformly rich or lean through the first three phases idle, off idle, part throttle...but a bit lean at WOT.
Remember: D-jet uses the stroke of the throtle valve switch contacts to add extra fuel. When the throttle is standing still...even at WOT, there are no enrichments from the throttle valve switch. This is NOT a throttle position sensor. It enriches as the throttle moves. If you are already riuch at WOT, the added injections can bog down, if you are driving with very quick, close together throttle movements...like on a twisty track. Sorry for the length...hope this helps. Ray
(1) a lean idle with a bump of fuel off idle, a rich or normal part throttle, back to a lean WOT. This is usually signifying that fuel pressure is correct or close to it...but overall spring tension of the center mixture screw is too light. It reacts too hard to the vacume ranges it needs to parrallel.
(2)a rich idle, a rich part throttle...and then lean at WOT...which generaly means one of two things. (A) the fuel pressure is approx. correct, the plate and chamber spring tension set from the center screw is approximately correct...BUT...the outer stop setting is too tight, not allowing enough stroke of the copper plate outward...to unload the stack...and move the rod in the armature. The outer cover plug...which is the outer stop, can only be adjusted at idle when the diaphram has been vacumed in. A good base setting to adjust from is to lightly contact the copper plate with the plug and start at 1/2 turn outward. Adjust and drive and check CO at WOT and move the outer stop about 1/4-1/5 turn at a time. Usually any adjustments of the outer stop equalling over 1.5 turns will leave you with a very rich flat spot off the line. (B) same situation as above...but if the outer stop requires having over 1.5 turns...then what is probably actually out of adjustment is the inner stop. That is the surrounding ring screw that the center main screw is screwed into. It contacts the keyhole intyermediate plate within. Between the outer stop screw and the inner stop screw...they dictate the total stroke ...and enrichment available to the copper load plate...with me ? So if you are having to adjust the outer stop screw more than 1.5 turns...it would be better to move the inner stop screw 1/4-1/2 turn out...to allow the whole plate assembly to vacume farther in...increasing the stroke...and allowing less adjustment to the outer stop. This will also entail about a 1/2 turn adjustment to your center load mixture screw to keep you around your baseline setting.
The object here is to getthe entire range of vacume reaction...idle...off idle..part throttle...wot...to be in one of two situations.
IDEAL: uniformly slightly rich or lean through all four phases. This would mean that a simple drop or rise in in fuel pressure of 1 0r 2 psi...or a 100 or so ohms more or less of CHT ballast would put you spot on.
You might find you like the ballast idea. If you use a variable potentiometer. You could give a very quick tweek right before you drive it to match changes in ambient temp.
NEARLY IDEAL: This actually might run quite a bit better depending upon th engine. Same as above...either uniformly rich or lean through the first three phases idle, off idle, part throttle...but a bit lean at WOT.
Remember: D-jet uses the stroke of the throtle valve switch contacts to add extra fuel. When the throttle is standing still...even at WOT, there are no enrichments from the throttle valve switch. This is NOT a throttle position sensor. It enriches as the throttle moves. If you are already riuch at WOT, the added injections can bog down, if you are driving with very quick, close together throttle movements...like on a twisty track. Sorry for the length...hope this helps. Ray
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Dave_Darling
- Posts: 2534
- Joined: Thu Apr 27, 2000 12:01 am
Alternative (better cooling) Fan for 914?
Greg, sounds like you pretty desparately need to tweak your full-load stop in the MPS. Again, Brad's page has just about everything that is known about these parts.
If that won't give you enough mixture, you might consider a rising-rate fuel pressure regulator (the D-jet FPR is adjustable but only regulates to one pressure), or at least an FPR that references to manifold pressure like the stock L-jet ones. That would throw you back into having to re-tune everything again, because it would affect the mixture across the board--but (particularly with an aftermarket non-linear rate FPR) you should be able to tweak that lean spot away.
I have also heard that enlarging the throttle body by ~2mm (or was that ~4mm?) can help with this. The theory being that the throttle body itself was a restriction on flow and the pressure in the manifold would start to drop again as the engine went to redline. I don't know, but it at least sounds plausible on the surface. I think (but am not sure) that this idea came from Rich Bontempi at High Performance House in Redwood City. He's got a ton and a half of experience, so his ideas just might be worth taking seriously...
--DD
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1974 VW-Porsche 914 2.0 (Type IV powered!)
Pelican Parts' 914 Tech Geek http://www.pelicanparts.com
If that won't give you enough mixture, you might consider a rising-rate fuel pressure regulator (the D-jet FPR is adjustable but only regulates to one pressure), or at least an FPR that references to manifold pressure like the stock L-jet ones. That would throw you back into having to re-tune everything again, because it would affect the mixture across the board--but (particularly with an aftermarket non-linear rate FPR) you should be able to tweak that lean spot away.
I have also heard that enlarging the throttle body by ~2mm (or was that ~4mm?) can help with this. The theory being that the throttle body itself was a restriction on flow and the pressure in the manifold would start to drop again as the engine went to redline. I don't know, but it at least sounds plausible on the surface. I think (but am not sure) that this idea came from Rich Bontempi at High Performance House in Redwood City. He's got a ton and a half of experience, so his ideas just might be worth taking seriously...
--DD
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1974 VW-Porsche 914 2.0 (Type IV powered!)
Pelican Parts' 914 Tech Geek http://www.pelicanparts.com
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914Racer
- Posts: 56
- Joined: Fri Jun 07, 2002 12:01 am
Alternative (better cooling) Fan for 914?
Dave/Ray,
Thanks for all the input. Fortunately my roommate is an electrical engineer in possession of an LCR meter so we've been messing with the MPS. We have adjusted the inner screw to richen things up at part and full load plus I have the full load stop backed out as far as possible without having the diaphram bottom out on the case of the MPS. We seem to run just a tad lean at full load but we're rich at idle. Not too bad though.
So, now to this weekend. We're at Thunderhill, it's 100 degrees out. After 3 twenty minute sessions of seeing 400+ degree head temps we dropped another valve seat. It happened in the pits on start up after a session, so no big damage was done other than another ruined weekend. I think our next step is to get it fixed and then tune it on a dyno so we can pinpoint our problems. This is killing us. It's no fun anymore.
Thanks again for all the help!
-Greg
Thanks for all the input. Fortunately my roommate is an electrical engineer in possession of an LCR meter so we've been messing with the MPS. We have adjusted the inner screw to richen things up at part and full load plus I have the full load stop backed out as far as possible without having the diaphram bottom out on the case of the MPS. We seem to run just a tad lean at full load but we're rich at idle. Not too bad though.
So, now to this weekend. We're at Thunderhill, it's 100 degrees out. After 3 twenty minute sessions of seeing 400+ degree head temps we dropped another valve seat. It happened in the pits on start up after a session, so no big damage was done other than another ruined weekend. I think our next step is to get it fixed and then tune it on a dyno so we can pinpoint our problems. This is killing us. It's no fun anymore.
Thanks again for all the help!
-Greg
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914URY
- Posts: 69
- Joined: Mon Nov 12, 2001 12:01 am
Alternative (better cooling) Fan for 914?
I molded in a dual outlet NACA duct into my fiberglass passenger door and ran a 6" duct thru the firewall to the fan. I have a picture of it on my PelicanParts member profile under "URY914". I can't really say it lowered the oil temp as I have only autocrossed since doing it. Let me know if someone wants more detailed info or pictures.
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ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
Alternative (better cooling) Fan for 914?
Greg, about how many turns out...from seating against the plate at idle...is the outer stop? It sounds like you have it out a long way. Running rich at idle is not too bad, but if your stop is too far out it will destroy bottom end. It sounds like you would get better transitions from throttle and shift if you made a small fuel pressure adjustment...to enrichen accross the board (like 1.0-1.5 PSI) and then backed off 1/4 turn on the center load screw to return idle and midrange to where you started...and then backed the outer stop back in 1/3-1/2 turn.
My train of thought is that if you are still a tad lean with the outer stop screw all the way out to its max....you have out run its avaialble range to adjust your fuel mixture within the baseline availability of fuel. That baseline availability of fuel is based on a fixed volume (thats supply volume and pressure from pump being constant X the injection rate). If the volume supply is constant, meaning no spikes/dips, and the injection rate is maxing...meaning you are at the end of the ability of the MPS to add fuel for more load, then the only way to get back into the middle of the scale is to dial in more fuel pressure...and readjust the outer stop of the mps. Just bear in mind that over about 36 psi...the stock injectors begin to have problems returning to their seats, and may have problems maintaining correct spray pattern. Also if the range or arc of flex of the copper diaphram is too great, it causes premature cracking.
The TPS is really only for transitional enrichment...while the throttle is moving, which is why it does not assist your mixture at WOT...cause the throttle is not moving.
One more thing. Your fuel mixture at WOT...or max injection cycle rate could be suffering from the inability of the pump to keep the lines full at the prescribed pressure. A 2 psi drop at WOT (which is common) is 5% volume loss. This is a multiple which changes with cycle rate. Its huge! I recommend a modified fuel pressure line accumulator...or better yet, at the end of the metal line passing through the body...put a large fuel filter. Move thepump to the rear, add another pump next to it. They will pull from th filter through a "Y" connector. Each pump goes to a separate rail. Simply remove the line from the other side of the cold start valve, plumb to the new pump. You have now split the rails off. The loose end from the cold start valve connects with a "Y" fiting to the return end of the other rail...and plumbs into the FPR. That way you have one common FPR regulating both rails, but with a separate volume supply to each rail. The fuel pressure remains rock steady. Huge difference.
When you accelerate on the stock system...you get the copper plate moving...trying to enrich...with a simultaneous, momentary drop in fuel pressure...which defeats the process, casuing you to have to run the overall fuel mixture higher than necessary in order to have enough enrichment whgen the coppeer plate moves...to prevent a flat spot. Sorry for the length. Ray
My train of thought is that if you are still a tad lean with the outer stop screw all the way out to its max....you have out run its avaialble range to adjust your fuel mixture within the baseline availability of fuel. That baseline availability of fuel is based on a fixed volume (thats supply volume and pressure from pump being constant X the injection rate). If the volume supply is constant, meaning no spikes/dips, and the injection rate is maxing...meaning you are at the end of the ability of the MPS to add fuel for more load, then the only way to get back into the middle of the scale is to dial in more fuel pressure...and readjust the outer stop of the mps. Just bear in mind that over about 36 psi...the stock injectors begin to have problems returning to their seats, and may have problems maintaining correct spray pattern. Also if the range or arc of flex of the copper diaphram is too great, it causes premature cracking.
The TPS is really only for transitional enrichment...while the throttle is moving, which is why it does not assist your mixture at WOT...cause the throttle is not moving.
One more thing. Your fuel mixture at WOT...or max injection cycle rate could be suffering from the inability of the pump to keep the lines full at the prescribed pressure. A 2 psi drop at WOT (which is common) is 5% volume loss. This is a multiple which changes with cycle rate. Its huge! I recommend a modified fuel pressure line accumulator...or better yet, at the end of the metal line passing through the body...put a large fuel filter. Move thepump to the rear, add another pump next to it. They will pull from th filter through a "Y" connector. Each pump goes to a separate rail. Simply remove the line from the other side of the cold start valve, plumb to the new pump. You have now split the rails off. The loose end from the cold start valve connects with a "Y" fiting to the return end of the other rail...and plumbs into the FPR. That way you have one common FPR regulating both rails, but with a separate volume supply to each rail. The fuel pressure remains rock steady. Huge difference.
When you accelerate on the stock system...you get the copper plate moving...trying to enrich...with a simultaneous, momentary drop in fuel pressure...which defeats the process, casuing you to have to run the overall fuel mixture higher than necessary in order to have enough enrichment whgen the coppeer plate moves...to prevent a flat spot. Sorry for the length. Ray
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914Racer
- Posts: 56
- Joined: Fri Jun 07, 2002 12:01 am
Alternative (better cooling) Fan for 914?
Ray,
We have already bumped our fuel pressure to 32psi. We occasionally run a pressure gage that sticks out of the rear deck so the passenger can watch the pressure as we drive. With our new front mounted fuel pump and K&N fuel filter we've never ever seen the pressure waver under any conditions. We also replaced all the fuel line with stainless braided lines. We will be very diligent in watching our pressures when we're on the dyno though, thanks!
As for the MPS, the way I adjusted the full load stop was by watching the LCR meter. I let the reading stabilize with the stop completely out and I slowly tightened it until I saw the reading drop by .01 or .02 Henries. At that point I figured the stop was coming in contact with the diaphram providing a positive internal stop. This way I ended up with the richest possible full load setting I could without damaging the MPS. Based on our LCR meter readings we should be way more rich than a stock MPS at part and full load.
-Greg
We have already bumped our fuel pressure to 32psi. We occasionally run a pressure gage that sticks out of the rear deck so the passenger can watch the pressure as we drive. With our new front mounted fuel pump and K&N fuel filter we've never ever seen the pressure waver under any conditions. We also replaced all the fuel line with stainless braided lines. We will be very diligent in watching our pressures when we're on the dyno though, thanks!
As for the MPS, the way I adjusted the full load stop was by watching the LCR meter. I let the reading stabilize with the stop completely out and I slowly tightened it until I saw the reading drop by .01 or .02 Henries. At that point I figured the stop was coming in contact with the diaphram providing a positive internal stop. This way I ended up with the richest possible full load setting I could without damaging the MPS. Based on our LCR meter readings we should be way more rich than a stock MPS at part and full load.
-Greg