performance mod for 16 valve 928?
 

Since performance chips don't exist for older 928s-- is it possible to manually rewrite the program for the earlier brains???? also , can performance fuel pressure regulators really make a difference?

there are other ways to achieve more hp..
headers, no cats, rmb... euro heads and cams can run you some $$$ but the bang is awesome

Ive already installed msds headers,y pipe no cat and borla kit. and k&n filter. I like the sound of euro cams!, are they compatable with americam engines????

The US motor has a lot of intake restrictions, smaller valves, smaller ports in the heads, smaller runners in the intake, and a MUCH smaller throttle with a tiny opening to the air flow meter. Exhaust isn't good at any stage either, but sounds to me like you have that covered.

I don't know if the US short block is different from the Euro, but the Euro motor is higher compression and not non interference. I do think the heads and cams will fit, just no idea on the results. What most do is build a hybrid with Euro top end and 85/86 US short block, or just build a complete Euro motor.

L Jetronic is much simpler than the LH, no chips to change that I know of, and no knock detection. I am looking very seriously to upgrading to a newer or better control system, either MegaSquirt or maybe a Euro LH system that would work with the sharktuner. Both options I guess would be easier than trying to reprogram the L from scratch.

Then you can always add boost, or just swap in a different motor, S4, or whatever your wallet permits.

Jim---

all heads are interchangeable with blocks, so to speak.

Just because they will "fit", doesn't meant you should or will.......

"If" you have Ljet injection (electronic injectors), you can use the Euro intakes/throttle body from the mid '80s (84/85/86) 310 hp engine. The heads, cams, intake, throttle body are direct replacement for the US pieces. Gregg Esmell has the complete set up (in pieces) on eBay right now. Don't know what he'll want for the intake system (bids start at 6 bills and didn't include the maf sensor), but he's offered me the cams and heads for about 1500. I would buy the heads and cams, but I'm sourcing them from 2 other guys....


hope this helps----


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Re: performance mod for 16 valve 928?
 

I haven't seen anything about anyone modifying the L brain, the earliest seems to be the 85 LH either US or more recently the Euro. Its just easier to start with a better brain, LH or megasquirt, reprogramming isn't trivial.

Fuel pressure regulators really can make a difference, mess with them and the car can run like crap.

I'm no expert and this could be all wrong, but the impression I get is that a skilled person can mess with the distributor in the old fashioned way to play with timing and advance and get very good results, but it won't be as adaptive as the later electronic systems and may need adjusting more frequently.

The weak link isn't fuel, its getting more air through the motor. Improve the air flow and the existing fuel system is good to about 350 hp. Above that a rising rate fuel pressure regulator can be used as a bandaid .

Thanks for the tips!! I think the logical next step would be to get my hands on some euro intake pieces.Is it possible to jump the wiring of the airflowmeter and remove it..and create a larger intake area??

Herr Kuhn used a box from SplitSecond to put a larger higher flowing MAF on his L jet turbo 928, but its not real cheap. The L jet won't run without something telling it the air flow in a way it expects.

Jim, whats your goal and your budget, might as well lay it all out for the best advice.

My goal is to achieve best performance.. with bolt on external modifications.on the cheap...like used euro parts or modified stock parts. To get my us car as close to euro performance as possible.

Cheap used Euro parts, :) Let me know when you find some.

Cams and heads each go for about $800 or more a pair, $500 or more for an intake and throttle, maybe double that or more with the fuel injection parts and LH brains. Most heads will also need new valve guides and other machine work.

928ram has a post here in the classified section for a complete early Euro motor, last I checked he wanted about $1800.

Everybody with a early car seems to be looking for Euro and more HP parts, so deals can be hard to come buy and not last very long. Some stuff advertised as Euro aren't, or aren't complete with US cams and or heads instead of the original Euro parts.

****** Something to consider. Boost.

Here is a recipe for power on the cheap. Find a good low mileage US 4.7L motor. Pull the heads and have some big intake valves put in as well as a bit of porting. Buy a Euro S pair of cams. Chop off the top of the US intake tubes, port them, and build a plenum box using them on the bottom and bolting up to a Kenne Bell type blower on top. Get some wide tires.

Jim---

now that Danglerb has said his piece again, opinions that he has, and seeing as how you guys didn't read my above post, here's the deal:

as I said in my previous post, Gregg Esmel has the stuff you're looking for.

heads (fresh with new valves guides---otherwise stock) and cams/towers $1500

intake (plenum and tubes for L-jet) and throttle body starting bid at $600

he also has a MAF sensor, warm up regulator, and probably injectors if you asked.


ram928 (another Jim) has the Euro stuff, but not the intake tubes----you need these to get the big bang. finding just the L-jet intake tubes will be near impossible, as no one in their right mind would sell just the tubes. you'll have to find a complete intake. besides, all of his stuff may be in my garage next month, if we can come to terms.....


If you want Gregg's number, PM me and I'll put you onto him.

Considering how limited the supply of this Euro stuff is, this may be the only way you can get the job done.


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And no Danglerb, you don't just throw in a big set of valves.......

Call Phil Wyatt and tell him about that----he'll laugh at you all the way to the bank.

On second thought, just install his 4 mm stem, titanium valves and his custom fab'd buckets, then add a Devek R1 cam grind to the mix and you get buckets of added HP.

Better bring half the bank's holdings too, if you go that route.


------

seriously Jim,

without going into the shortblock, your selection of avenues is limited.

your's is already at 220 or so, so to get just the 300 number, you must use the entire Euro list of pieces, regardless of cis (Euro 300hp) or L-jet (Euro 310 hp). This will cost you the numbers I've quoted in my above post (about $2200-$2500 if my memory serves me correctly), plus TB and H2o kit ($600), and your labor, and any other misc stuff that needs to be handled in the swap.....

Here's the rub.....

you can buy one of Carl Fausset's supercharger kits for about $6000 (or less--I'll have to recheck), and it's a bolt on deal.

Everything is included in his "complete" kits (he has incomplete kits as well) to get you into the near-double the HP with bolt on parts.

Think about it before you start pulling heads and pulling this......half the money will only get you 50-70 hp, and you have to pull the motor apart. Twice the money will get you "nearly" twice the hp, and you don't have to pull the heads, change out the TB and H2o pump, and it idles like a stock engine until you gas on it......

The labor cost/time for either way you go is nearly the same, probably less by just adding the supercharger.

unless your engine is in need of head gaskets and lower end work, your really dollars per hp ahead if you just go the supercharger route......

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Jim...I have a set of fully ported 84 US heads I'd be willing to sell.

If you're on a budget, get a set of 78-79 cams. Much more aggressive than the 80-84 cams. You already have the headers/exhaust so an adjustable FPR will help if properly dialed in w/ a wide band sensor.
If you surf the other Porsche forums, do a search for AFM-944. A FR Wilk had a nice website detailing the inner workings of a DME (somewhat similar in function to the barn-door AFM of our L-jet cars).
I may add that in order to get 300 hp from a euro set up one needs EVERYTHING from the donor car... fuel lines (which have a larger internal diameter), pistons (which have a higher C/R), etc. Just the intake and cams are not enough.
With used parts and some ingenuity you can build an SC system for around $2k.

WOW im learning something here....well i believe the stock '84 arrived with 242 hp (even more torque) with all the emmisions bs..all that is gone.even the belt driven fan.. freeflow exhaust and k-n filter with small airbox mods.. im guessing hp is around 260 + so im just looking for around 50 hp.No supercharging or nitros or turbo...Plus i dont think its a good idea to put too much stress on my 100000 +mile engine and tranny (auto). So will a huge air intake increase(euro intakes and throttle) give me 20 hp? it sounds like a good step. thanks JIM

100,000 miles it is just getting broken in

100k engine and tranny should be fine. You aren't even remotely close to the power limits of the auto trans.

84 US is 234 hp at the flywheel, 84 Euro with a LH and Maf is 310 , but thats no cats. Headers and high flow exhaust add around 20 hp, K&N subtract from wallet, but don't add HP. Pulling the airpump might be good for 5 hp. Mark Kibort posted a run down of what changes were made in each stage of mods up a Euro hybrid.

Until you improve the flow through the heads, (valve size, port size, and cam) I'm not sure what improving the intake will do. Throttle and air flow meter are pretty small though.

Is it possible to modify a -85 mass air sensor to run with -84 intake??In place of the stock mass air flow meter...(to eliminate restrictive size).Ive already found an 85 airbox bottom used.

The old barn door system in the pre 85 models has a vane the air moves, like a barn door, attached to a potentiometer and it sends a raw voltage from that and a temperature probe to the L brain. A MAF is a hot wire system with a bunch of electronics needed to control it.

Told ya about this in my earlier post, you need a MAF translator box like the SplitSecond PSC1-009 Herr Kuhn is using, and even better you don't need an $800 Porsche MAF you can use a freaking huge $150 GM MAF if you want.

http://www.splitsec.com/

http://www.splitsec.com/spike/Porsche-928-Turbocharged/spikePorsche928turbo.htm

If you want a place to start, look at the throttle body, the US is a tiny thing, but plan on needing to change the whole air path for real gains.

ok, that translater box looks interesting...and a GM MAF can work? Have you seen this? if so do you have an idea what car it was from?- part number??? Any other cars with similar MAFs..that would work??VW- AUDI -BMW-???

JIm...I have the recipe for the MAF conversion. Contact me if you are interested.

You know the old saying many ways to skin a cat?

Well there are MONEY ways to increase the HP of a 928. ;) But freaking nothing is cheap or easy.

The link in the message above shows Herr Kuhn's car with the MAF.

In theory any MAF could work, but the translator has to be calibrated for it, and the GM is the biggest, cheapest, most reliable unit and the calibration is already done for it.

thanks Danglerb!....i checked out the split second sight and Kuhns application. i like the idea of the gm maf....i would need the PSC1-009 translator???I could afford this...about $350 total?? Again do you know what auto this GM MAF is from???would my existing wiring harness fit the translator or is modification need there too? I would like to improve this area of intake and probably stop there for now.Leaving the rest stock .Possibly replacing throttle body down the line.( possibly T.B. from euro 4.7 or 85-86 u.s. 928).

Mr. Kuhn i would like to see your MAF solution....have a link or email????:)

I would do the MAF last as its a tuned element, and might need to be fiddled with all over with each change you make later. Which MAF they use is explained on the site.

Its really half a dozen things that make small changes that add up. Without the heads and cams the rest may feel pretty small on there own.

Lot of really ignorant advice in this thread.

Perhaps all you rocket scientists can explain why my 83 US 4.7 has run a best time of 13.44 in the quarter mile with a US fuel and intake system?

20 hp for a full header/race exhaust? Yeah, right. Try more like 40 to 50.

And no one (that i saw) mentioned lightening, which is BY FAR the cheapest- and one of the easiest- way(s) to make any 928 faster.

Taking a 3250lb 928S down to 3000lbs is like adding another 25-30HP, but even better, it also aids handling and braking to boot.

Full exhaust and reduced weight to 3000lbs (easily doable while maintaining a 'full' interior), and you'd run door to door with an 84 Euro.

Last Euro i raced was an 83 with a 65hp shot of nitrous and i beat him 3 runs in a row. He used to post at rennlist and 928S4VR as "Lance".

Thanks for another point of view m21 sniper...i decided to go with a AFM replacement, to a MAF and split second convertion hardware...i think just tossin out that piece of SSSHHH AFM is gonna make a large difference. I was debating throwing out my rear seats, console and carpeting...100 lbs there??

Euro envy isn't pretty.

Not my fault stock Euros are slow.

There are numerous weight savings threads on 928s if you browse the net. Hehe, i've authored a few of them. Mine wieghs 2900 lbs and still has a 95% complete interior.

Thats about 400 lbs isn't it, what did you take out?

My guess is that some "stock" Euro's in the US may have suffered in the federalizing process. Catalytic converters and some kind of O2 sensor feedback system piggybacked onto the factory system. Getting the 80-83 CIS cars to pass smog might have been real nasty.

Come on Sniper, tell us the truth, it's the hamster isn't it?

I've raced three other 928s. An 85 US (theeney, former poster at 928S4vr site), an 83 Euro (w/65 shot of nitrous- Lance from rennlist), and a 83 US (racegal from 928s4vr site).

I beat the stock 83 US by 12 car lengths in a quarter mile (5 car length spot up, and 7 lengths at the finish line). Hehe, i guess it is the hamster. :-P

I found the 85 US and the gassed 83 Euro to be identical in performance. I beat both by about 2.5 lengths from a standing start, consistently.

Among the items removed are all belt driven accessories (and associated brackets) but alternater, the entire stock exhaust (which is in itself darn near 100lbs) and replaced it with a 22lb front to rear custom 3" borla single exhaust, the factory battery with a miata battery (12 vs 42lbs), the jack/spare/pump, the belly pan, every other fender bolt, the grill, the rear wiper motor and arm, the rear visors, all the broken down and useless interior sound deadening goo (40lbs worth, i weighed it), the obsolete factory amp, the cruise control unit, the entire A/C system, and a bunch of minor brackets and fasteners from all over the undercarriage.

A lot.

And yet, i still have a fully equipped interior:

http://i22.photobucket.com/albums/b3...rMarch06RT.jpg

I Guess you dont need A/C up there like we do in Florida!!

Hehe, actually, no, didn't remove the alt OR the P/S. Everything else though :-P

Tell us the truth. It's the hamster!

I had a rat under the air filter box, does that count?

Deja vu anyone?

Hey Sniper!!!

when you gonna lose those phone dials, for another 44lbs of diet on your 928??

I just thought it was pretty good of you to bust on everybody about putting the 928 on a diet, but------

My 19 incher swap resulted in 44lbs of UNSPRUNG weight reduction. Yes, I weighed each of the 16 inch 993 style wheels and 60 series tires--compared to the 19 incher set up-- and it was a whopping 44 lbs!!

Being as how you are a proponent of weight redux, you should know (I suppose you do....) that weight redux of the unsprung variety has even more benefits than just throwing out the back seats, the passenger seat, the HVAC system and anything else you can do without.

Mmmmm........ I recall posting some pretty interesting correlations about unsprung weight reduction/hp--performance gains, so do your research, my friend, read my posts about just what you get when dump those antique wheels and tires and get the new stuff on your rig!!!

(You'll find that 44lbs of unsprung weight will give you about nearly 33% more performance [relative horsepower] in my case.)


Of course, this will just be another theory for you guys (Mule, Danglerb, and the like.....) to argue about.



P.S. I just purchased a set of Hooker header sidepipes (like the Corvettes used in Can-Am racing years ago). Couple these with any of the available headers, and you'll answer another issue----How do you put a big free flowing exhaust system on a 928 and lose weight doing it? Header sidepipes----The side tubes [4 inchers, they are] are removable, with slip in mufflers for street, without muffs for race.

Mmmm.......Can you say "German Corvette"?


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And I have no doubt that you can back up this 33% performance increase. With your infallible word!