Newb 944S LS1 Conversion

GB,

In general your VSS mathematics look correct with the minor exception of value precision.  There's no accuracy benefit in using a 12 digit Pi if all the other values only have precision to 3 or 4 digits.
Fortunately in this application I don't think it matters much.  

I whole heartedly believe correcting your VSS settings should improve drivability as the CPU needs to know the correct relationship between engine speed (crank position sensor) and vehicle speed (VSS), however I have my doubts that VSS corrections will do anything for your idle issues.

You really didn't elaborate on your idle issue, but barring any ignition system problems (like bad plugs or wires) the common causes of rough or irregular idle conditions are:
1) Vacuum leaks
2) Faulty idle air control valve (idle air sensor control motor)
3) Any air intake that might bypass the throttle plate (IE PCV and Purge Valve vacuum sources)

So far I have about 10 seconds of idle on my engine at 1000 rpm but it was fairly smooth and I have a "sizable" cam:
COMP Cams LSR Cath. Port
Lift: .617/.624 (intake/exhaust)
Duration: 231/239 @ 0.050  
Lobe Separation: 113 degrees
This cam is a little bigger than the GMPP HOT CAM and a little smaller than the Lingerfelter GT11.

Factory LS1 Cam:
Lift: .467/.479
Duration: 193/201 @ .050"
Lobe Separation: 116 degrees

Good luck with the "sorting!"

You indeed caught me on a couple details. taking pi to that many digits is just something out of habit and always enter all of it to that many digits as have been doing since had a pi digits competition over 20 years ago. just stuck with me.

in my actual calculation i carried all digits through to the very end and merely rounded to last digit for each field i had to put it in for the table. doesn't swing anything either way. i glossed over this in  the explanation as i was mainly just trying to illuminate a path that might be veiled to others some time in the future for other 948 conversions.

In my case, i have zero issues with the car just idling on its own. The issue i have is coasting up to a somewhat quick stop at a stop sign or red light and watching the rpm cave all the way down to 200 or so and then suddenly awakening back to a normal idle. which is truly a dead ringer for VSS issues.

my cam is definitely bigger than stock with the following parameters as highlights from the following link. definitely not as big as yours but also if i recall i think your running a newer and bigger brother engine to my '97 c5 ls1.

competition cam

lift: .566"/.568"
duration: 222 intake / 224 exhaust
LSA: 112

supposed to be tuner friendly cam and quite driveable. with my 2.5"/3.0" flowmaster Y i find the scavenging makes it sound quite dual exhaust sounding and gluggy enough for my liking. although my borla on the end gives quite a rasp on decel especially i actually like it and gives me great smiles per gallon. couple nights ago took it under a couple underpasses with a breif hit of WOT, literally giggled out loud by myself like a madman! probably ticketable lol.

Hotrodz of Dallas wrote:Sounds like exhaust moisture. What header gaskets are you using?

after your couple replies with the issue i am facing, i got motivate and ripped the engine bay apart to not only take finger swipe samples of the wet spots but also to get at the exhaust manifold bolts (which are a 13mm not a 10mm as i had incorrectly referenced before).

what i found astounding and worth sharing was that the fluid dew'ing on the bottom of ports 5 and 7 of the manifold were of a darker coloring so definitely was oil. Yet not completely oil because with the watery feel and low amount of viscous feel to the fluid you could tell it was more moisture than oil and with it the smell was that of unburnt fuel which matches the hackjob tune in my ecu that has significant more timing advance and fuel added (no knock monitored at all though, so just seems a tad sloppy on the overall 3d contour map of the timing and fueling).

i was able to get an extra quarter turn out of the back four bolts vs. none out of the front bolts so i think i may have solved the issue completely, but only time will tell when i get another testing registration permit to try it out and see how all this worked out after i come back from holidays. Also got one tiny minor seep from the rubber end cap cause i failed to gasket seal the metal cap on the end of my transaxle after adding the stiffening plate. But 90% of the gear oil seep went away after epoxy'ing the thread of the one and only bolt that is not captured in a pocket of the casting of the transaxle.

getting closer....
will need to adjust clutch again and get the MAF to respond by ohm'ing out my suspected disconnected pink wire that feeds it switched 12V power when i get back. will update then for sure.

Thanks all!

I highly doubt that the Vss is the reason for your rpm drop coasting down. I’m betting a good tune will take care of it. I’ve been fighting a stalling problem on coast down on my wife’s 04 Pontiac GTO. It have a pretty big cam and the last tuner I had tuning it, messed up some parameters. I finally figured out what he (a pro tuner) messed up. Vss wise, this car is all stock drivetrain and tire size. So I knew it was not a Vss issue. Get yours tuned properly and I bet your issue is gone.

Your overspeed and underspeed tables in your adaptive idle need to be adjusted. Basically your timing at idle or 0 tps. Too much timing is being pulled at coastdown, and the adaptives are not adding back enough to compensate if that makes sense, when the throttle blade is closed. Sounds like you have hptuners. Easily corrected if you log the correct parameters.

Leva wrote:Sounds like you have hptuners. Easily corrected if you log the correct parameters.

Yes definitely have hp tuners and about to buy my credits/tokens to begin being able to write to the ecu as I work through some of these gremlins. Once I get maf to respond I will look at these tables and such and take a log off everything and probably post on datazap with a link here for more input.

I've never tuned from scratch and even then the variance on timing the previous owner did on this aftermarket can seems a little heavy handed but yet no knock.

My only experience on tuning is on my boosted frs with rom raider and even then only did augments on my final email time on the kit with open flash tablet to which shiv pathak did the first seven tunes based on my logs.

Obviously an NA V8 is a totally different animal.

Not sure if I should just flash back to stock tune I found on hp tuners and go from there instead of this jacket tube for the cam from previous owner. Not sure if that adds or deletes problems or just removed power he already found with this cam on timing advance and more fuel.

Leva wrote:Your overspeed and underspeed tables in your adaptive idle need to be adjusted. Basically your timing at idle or 0 tps. Too much timing is being pulled at coastdown, and the adaptives are not adding back enough to compensate if that makes sense, when the throttle blade is closed.  Sounds like you have hptuners. Easily corrected if you log the correct parameters.

have a look at the pictures below when viewing the two files in difference mode within VCM editor (hptuners)

differences show up in green on dialogue boxes and no changes are blue.

i opened the overspeed and underspeed tables which were blue to verify 0 differences and all values show just that with difference view engaged. so modified tune presently on car is the same as stock ecu tune for these two sets of underspeed and overspeed tables in the adaptive idle.

my question is whether the presence of the more aggressive cam requires adding of timing by a bit for the idle underspeed spark vs. rpm error table. to which i would think 0 change for 0 rpm error and as the rpm error increases to the negative then timing increases slowly and linearly to say maybe +4 by the -300 mark?

or perhaps this is the wrong approach and since the tables between modified tune and stock have 0 differences on adaptive idle underspeed, maybe this is not the problem for a sag of throttle to 300rpm when coming to a coast at a yield or stop/red light and should try the vss parameter write fix to overwrite the previous modified numbers in this rx7 swapped ls1 that has now been swapped a second time into my 948?

open to suggestions.....

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Post your tune file and a datalog if you have one. I'll take a look at them.
Also, give me your cam specs.

How does the car idle right now? Without any throttle input? Did you swap cams when you did your swap?

So while taking care of a couple things to ensure car would be ready for inspection, ran into some issues during a test drive and did a log to see what's happening and checked the codes.

I have a P0463 on fuel level send but I think that's rather benign as the porsche fuel send is completely independent and most likely just need to turn that off in the tune. But the real problem was misfires detected on cylinder 7. While logging while running cylinder 7 was racing through the misfires as if it was a counter so wasn't firing at all.

Did a coil swap of 5 and 7 to see if misfire would move, but no dice, checked the custom plug wire which seemed extremely doubtful since i was quite diligent on the terminations with the new taylor spirowire and with the specific crimper its really quite trivial and nothing tedious. not the fancy 25ohm like oml or msd wires but sitting at 300 ohm which is the same as stock wires from what i could tell. pulled the plug and looks like previous owner of engine had a mish mash of original denso factory plugs and some replaced with NGK iridiums. definitely all fouled up and oily as hell.

my bad for not noticing that or checking when engine was on the stand and paying it for now. quite the headache and difficulty to pull the spark plug on cylinder 7 amongst exhaust, steering linkage and hydroboost hiding it from above. without a 4 post lift to adjust working height i'd say this is next to impossible. also took the time to readjust the plug boot on the wire as i noticed that there was no unclick of the connection on spark plug and when putting new plug in and tightening and then putting wire on i got the definitive click on the end of the spark plug.

started up while monitoring with hp tuners and immediately throttle response was much much smoother and sounded far healthier.

went for test drive to take the following logs i have attached in both hpl and csv format since i have no idea if either of you guys (Bob/Leva or anyone else) specifically has hptuners or more specifically VCM scanner to take a look. I still get some misfires on 7 mostly and occassionally cylinder 2 as well but i plan to preemptively change its plug as well and just see if that clears up.

On the drive i noticed a couple more things before I answer a few of the questions above. On an acceleration close to 6000rpm and then full decel i get the occurence of blue smoke but never any other time at idle or normal driving. A google of this tells me i have some failing valve stem seals and of course with it being on cylinder 7 and most likely 5 i will have a significant future teardown job to get acccess to that valve cover with hydroboost. honestly can't complain too much cause i'm still quite thrilled a great deal has actually worked to this point since i am merely a forum mechanic learning by doing and had never done a swap before. This is a far better issue than having failed rings which would be a complete reset on dropping the engine. I think this also explains why i have an oily condensate drip on the bottom of cylinder 5 and 7 exhaust manifold tubes. It has drastically reduced since cylinder 7 is now firing but until said valve stem seals are replaced this will not go away to my understanding.

Next observation is that my intake air temperature goes nuts if i sustain more than 3000rpm. I believe this is partly cause I decided to go the road less travelled on not hiding intake under the nose panel to have it more accessible and not having some form of heat shield. Already purchased a form-a-barrier sheet from DEI with their cool tape and some top bulb seal weather stripping to form this as a walled barrier in engine compartment in the driver front fender headlight area. Should do the trick.

for cam specs, look in previous post called "clarifications" i have the phrase competition cam in bold and that's actually a hyperlink to the full specs on summit racing as opposed to the abridged specs i gave.

now to answer some of leva's questions, i was going to change out what i thought was a LS1 cam for an LS6 cam a buddy gave me for free when he replaced his with a bigger one. But when i pulled the old one out, to my surprise it was this competition cam that the previous owner never told me he did. He just simply told me rebuilt the top end of the motor when he got it for better sleep at night sake for his rx7 swap while he had the motor out. as such i literally just put the cam right back in and reset the timing arrows to be perfect and took out my lifter dowels and put the timing cover back on. I figured it was a safe assumption that when previous guy did the cam he HAD to have changed the springs since a cam of this spec could never possibly work with stock springs if was going to change them for the LS6 cam. So in summary the tune the previous owner had on this had always worked with this cam, assuming his take on the tune wasn't a brute force hack job which by looking at some of the relevant tables there's a significant add compared to stock tune right across the board. i'm posting a factory 2001 f body tune to be able to see these comparisons more easily from the as found vs. factory.

even with the 7th cylinder missing idle from start and start has never been an issue (no throttle input). I will definitely say though that now with having cylinder 7 back the idle is smoother and even more noticeably a quick rev of the throttle is much much smoother. Absolutely 0 backfires on accel or decel now.
And to that end on yesterday's test drive i noticed the sag of throttle when costing to a stop much much less and sometimes not at all really.

and after typing all of this i just realized that host an image is merely just that, for images and won't allow me to upload csv or hpl files. I doubt renaming them falsely to jpeg's is going to be a workable workaround... not sure if said files can be sent through PM's on the forum either.

since i have your email Bob i will just email it to you, Leva send me a PM with your email if your curious as well for the tune files, hpl files, and csv files. same to anyone else who is reading with interest but has been silent on replies. nothing exlusive here, and who knows could help someone else huge in the future.

Glad it's running better.

I do have HPTuners and VCM scanner. Use them all the time. email them to me and I will take a look.

Ultimately you need take care of any mechanical issues (misfires etc) before you can successfully tune, otherwise you will just be chasing your tail. You would be using 02 sensor/fuel trim histograms in the scanner to dial in the tune or fueling. With missfires and sky high iat, the data you are logging is useless. My advice would be to grab a stock LS fbody tune from hptuners tune repository and start from scratch since there are so many unknowns. Goat rope garage on youtube has some good videos on how to setup fuel error histograms in the scanner so you can dial in your maf and ve tables.

Here is an idea on how to setup your intake to reduce iat numbers. This setup significantly reduced my temps which is very problematic in these swaps. High iat numbers rob a ton of power because the ecu pulls a bunch of timing. Also can cause knock if your tune is off.[You must be registered and logged in to see this image.]

agreed on order of things to tackle but with cylinder 7 plug changed and those misfires largely tamed down and some help from Bob, my as found tune had wrong injector data in the tune.

it's like the remaining few misfires i see at idle and not at throttle are resulting from this.

i do have a copy of a stock 2001 firebird tune that i pulled from hptuners repository so i have that for comparisons. still highly likely i will abandon the previous owners attempt to dial in this cam with this as found tune that seems to be plagued with a hack attempt of increasing power.

when i made the exhaust i welded in an extra bung for a wideband which i will need to move on to the point of dialing in MAF and VE tables.

should be able to get IAT under control with the DEI build-a-barrier formable reflective foil and weather stripping to the hood for a heat shield. thanks for posting the pics of your heat shield, i plan on doing something quite similar to it. i'm quite intrigued how your tight 90 off the throttle body completely clears your hood latch. i had to trim mine quite extensively and even then it has a subtle dimple from the trimmed hood latch on fitment. i have a slight additional obstruction to deal with in that i relocated my coils right to the left of the coolant reservoir but the formable reflective foil barrier should help with making a crazy shape for a shield to block it off.

Look up smokeshow's method of simultaneously tunning maf and ve using the gmve equation in hptuners forum. Saves a ton of time. Basically uses stft error to dial in closed loop. You can then use your wideband to get your pe and wot fueling sorted. Inoriginally used the old school maf failing/stft + ltft method that takes forever with a ton of data logging. With this method, i got my last swap sorted in a few logging sessions. This method also gets your drivability, off idle/tip in fueling closer because your tuning with the o2's which ultimately is what the ecu is using for most fueling anyway. But the wideband is imperative for open loop wot/pe fueling.

Got to use the car a few more times before winter permanently set in and then got distracted by busy season at work and my other cars starting to complain with work they needed done (SCR/DPF delete on wife audi q7 tdi and more coil issues on my boosted frs).

with that outta the way and some new savings to blow on car parts, its time to get back to work on the Vorsche 948. Gonna order my AEM 30-0300 wideband kit with the hp tuners pro link cable so i can log it and use the tune that Bob gave me to copy/paste those values into a clone of my existing tune on the car.

But before i skip to that i am gonna replace my valve stem seals, change oil, and most likely replace my o-ring on my hydroboost as per Raymond P's writeup that i am most likely getting a sweat from. I have to pull hydroboost off to get access to cylinder 5 and 7 anyways for the valve stem seal so i'll have it right ripped apart to check and potentially replace that o-ring since i believe i bought mine when that was an issue.

so with all that comprehensive updates here's some pics of the last thing i got complete with some DEI Form-A-Barrier that worked out quite well after i made at least a dozen cardboard templates before i got the form fit to an acceptable point that i could take the $70USD plunge for the make/break cut wit the utility knife.

IAT was significantly brought under control with this fabulous barrier to which i was originally seeing on a hot 28C day upwards of 62C on IAT which is nuts. Although it was slightly cooler after i had the barrier done at only 20C the IAT only got up to 34C in the heaviest of stop and go and cone filter was quite cool to the touch. Works for me. bubble seal was straight off amazon and worked great.

Next up is changing my 17" silver turbo twists that i got off of a 986 on kijiji to gloss black while doing all the above work. Then hopefully some paint correction to atone for the moron who hauled the car in its dead form by putting straps across the paint that vibrated a line down to the metal and getting AC lines done.

Cheers.

will have pics of wheels soon.

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