What would it take to safely run a 930 at 1 bar on the track?
 

Ok, I am all over the place. Plan to rebuild a reportedly recently rebuilt motor due to a busted dilivar head stud and pitting on one cam. Part of me says to do just what needs to be done, and get back to driving.

Part, says to make to motor as bullet proof as possible and turn up the boost.

Prior owner was running 1.2 bar. I run 0.8 as I didn't want to grenade the motor...

Car has updated fuel head, oversized inter cooler, modified k27 turbo... Boost dial.

Prior owner said he got 400 hp out of it. I have been babying it, cause that's my nature. Kind of a low risk guy in a sense...

Turning down the boost, has caused rich afrs under boost, was going to adjust the WUR next...


But now, since I will have most of the motor apart anyway...maybe I can finish what the po started.

If I add super tech head studs, arp rod bolts...

Can I safely enjoy 1 bar on the track??? Not looking for crazy horsepower, but 1 bar would probably get me 375 hp... Which could be a bunch of fun on the track.

Would I need to do anything else? Just flow check the injectors?

Already added a front cooler and it runs quite cool...

Can such a motor last 50,000 miles???

Armchair quarterbacks, chime in :).

Check my specs below. I regularly run 1 bar at track. Not always, but often - as required (EBC).
I have had no mechanical breaks. No broken rings/studs etc. I run AFRs as high as 12.5. Sometimes more - but I would prefer no more than 12.5. I am still struggling to get enough fuel at 6000rpm.
I ran 1 bar with the stock IC - but sprayed water over it - same reasons as you state. I don't want to destroy the motor. Most of what I do to it is to try and preserve it. I have upgraded to 964 IC. For performance and longevity. But these engines are tough and 1 bar is no issue as long as you are sensible. I used to worry about EGT - the dial was always pegged. So I disconnected it. ARP rod bolts would be useful, but not essential (I am still running stock). I think they are more important for high revs rather than boost, and I limit my revs.
Regards
Alan

I ran 1 bar all day hard on the track with my street 930. It was super fun with DOT tires
3.4
SC ish cams
twin plug
boat tailed the webs
crank fire
big intercooler
front mounted oil cooler
Kendall 50w



http://forums.pelicanparts.com/uploa...1501976486.jpg
http://forums.pelicanparts.com/uploa...1501976496.jpg

You have a larger intercooler so 1.0bar is safe.

Alan the -007 will support 500hp but you need dual 044 pumps and set the system pressure at 100psi. For 400hp there shouldn't be any issues, may need to turn it up 10%.

Thanks guys...

My afr is 10 at 6000 rpm and 0.8 to 0.9 boost.

Chased boost leaks for a long time, never found any. Really think the prior guy just set it all to run 1.2... Was going to rest the boost pressure on the WUR...

I'm not brave enough to run 1.2 bar...

I assume you guys are running arp or similar head studs???

Or, stock steel?

At what point do you "need" arp?

The arp rod bolts would be more of a safety measure in case of over rev...

The stronger head studs help with high boost but also high rpm. There are better ways to make power than just increasing boost. If you keep the standard redline and top off at 1.0bar stock studs should be fine. If you have to rebuild the engine anyway then add the ARPs for peace of mind. We put them in every build where the studs are replaced.

I have ARP studs. But never broke any prior to replacing, that I can recall. Just replaced with ARP because I was in there.
Brian - I maxed out the flows on the 007 head, until one would go no more. There may still be a bit left in the other 5 but I dialled them all in to balance with the lowest flow. No more adjustment. I had increased the flow about 10% over what it was set at when I got it back from the mods.
Regards
Alan

What fuel would you plan to run if you did carry through with sustained 1 bar?

Well, I was hoping simply premium.

Race gas around here is $10+ a gallon. More at the track...

Do I need race gas?

Would love a knock sensor :)

I have been running 1 bar at the track for years without any issues. Stock motor with a K27 , larger intercooler, cold air intake and headers with a zork tube. I always run 110 octane race gas as added insurance against detonation.

I'm running our highest grade pump gas (98) which I think is equiv to your 93. My other option is Av gas - but the lead kills the AFR probe. Quick.
Alan

Efi with knock sensing would definitely extend the life of the motor. 1bar is peanuts

Sent from my SM-G950U using Tapatalk

There should be no problems and no special fuel needed to run 1.0bar at the track. Only caveats are running too much timing or high AFRs. Big intercooler should keep temps down.

Alan something isn't right if you've maxed out the -007 at 370whp. Shoot me an email and maybe we can figure it out, don't want to highjack this thread.

My timing is about 26 degrees at 5000 rpm, with a 15 degree retard under boost. Which I figure is really conservative... I have the msd boost retard, set really conservative...

Taking my motor apart I see I do have the black euro fuel distributor, which is supposedly the better one...

Under peak boost my afrs are 10 or less...working on fixing that...

Previous owner clearly did work on the motor.... He ran a lot of boost... It's probably easier to run more boost than undo all the work he did...

I kind of wonder if I have arp rod bolts already...

Yeah, at 15 degrees, you are super conservative.

As long as you have a big IC and keep the AFR's in check, enjoy the added power.

For reference, I see only 10 to at most 15 degrees of inlet temps over ambient at temps.

Meaning, our IC designs allow a very safe margin.

If you have ARP bolts already you will see a 12 point head (star like) on the nuts, and ARP is stamped in small letters on the bolt head. You won't see the bolt head - but maybe with a small mirror and torch if you can get down the case hole .
Brian, I will shoot you a PM.
Regards
Alan

make sure the engine and IC are sealed very well.
any air leaks is air that is not being pulled thru the IC. engine air leaks are worse as hot air is pulled in.

these are tough engines, the problem is over boost results in broken rings and there are a lot of engine running with broken rings and don't know it.

How would you know you have broken rings? If the leakdown is normal, can you assume the rings are fine?

From reading here, no, unfortunately.

Some have had ok numbers but the rings were broken.

Before my motor grenaded -
12psi of boost
Stock head bolts
Reground SC profile-ish cams
3LDZ
B&B Headers/Exhaust/Intercooler

I dynoed the car before badness happened it and it put 337hp to the wheels, with 100F+ intake temps before the intercooler.

Initially I thought I had just puked a turbo but before I put in a K27/K29 did a leak down, bad news. When I opened the motor I had a bunch of broken rings, this was likely my fault though.

New build adds:
Twin plug heads
SC-ish
crank fired ignition
knock sensing
RPM switch/adjustable WUR
EBC
K27/K29

I hope to run a bar safely but I am super paranoid I wont be able to fuel it. But I feel allot safer with a .5 WG spring, EBC and knock sensing regardless.

I guess if you just have a broken recent ring, it may not show up - basically you have just moved the ring gap to somewhere else on the piston. As the ring slowly grinds itself to bits, it would open the gap up. Add a few more rings and something would start looking suspicious. That would be my guess how it would play out with leak down.
So it would possibly take more than a single recent ring break to become suspicious.
I have been running mine at 1 bar on track for about 7 yrs. I have lost count of times engine torn down for mods etc (3-5). Never had a broken ring. The boost alone won't do it. Keep the AFR and timing in spec and you should be good.
Regards
Alan

Then how do you know? The threads I read mention leaving the piston in the cylinder with a rebuild, so you don't disturb anything. If you "look" now you committed to new rings, honing, maybe pistons, and heaven forbid its Alusil---new pistons and cylinders...

Whats the harm to running with broken piston rings if leak down is fine? Cylinder scoring?

Why the damage? Sounds like you had low boost?

How does one add knock sensors? Can't find anyone selling this for a 930?

Alan, did you simply reuse the rings after each rebuild? Can you peak at the rings, and if fine, put it all back together???

I am starting to understand this slippery slope thing...

I see rings for sale for $200 for a set, and $1000+ for a set...

If you put the best of everything on a motor, you an easily spent $15-20k on just parts!!!

You can re insert your pistons if you pull them out, with the old rings. The rings move around a lot. I once pulled the engine down after about 2 short runs from a rebuild (ie about 30mins running). The rings had moved all over the place from where they had been set. I posted a pic somewhere on this forum - of before/after.
The issue with running with known broken (or unknown) rings is they eventually damage the piston and the bore. If you search enough threads you will find pics.
If you don't have reason to suspect any ring damage, you can extract the cylinders and pistons intact - ie leave them as a unit.
Regards
Alan

Alternatively - if the ring land gap is in spec and the current ring wear warrants it (ring gap) you can re ring the piston (since you have it apart). I just used the scotch brite hone method (you will find plenty of threads in the 911 engine forum). Never had an issue with them seating OK. Word of caution - many of the new ring sets seem to end up with a ring gap already at the high end of wear spec. Don't ask me why. But if they are nicely within spec, maybe best left.
Alan

The 3LDZ gave up the ghost initially, but before proceeding a leakdown showed a pretty bad cyl (there is a thread here somewhere I started).

I believe that the car was running more than 1.2bar in most street situations. I think this for a couple reasons -

1. The car usually would bang off overboost switch. When it was on the dyno the IATs were so high I think that that's why it was only seeing 12psi.
2. The TiAL the PO was running had two red springs, while that should equate to 1bar it does not account for the headers. TiAL wants you to run .2 or so lower than your target boost level if running running headers/free flowing exhaust.

There are a few different options for adding knock sensing. Now this is my opinion, but if you want to be safe and run higher boost levels, go to stand-alone. Do not pass go.

Now you can also go the route I chose (which I am already regretting and the car hasnt even started for the first time) and thats an XDI-2 system to handle ignition.

JS also I believe also makes a add-on system which can be used on a 930.

Plan to disassemble long block Friday...

Need to see if I have Alusil or nikasil from what I gather...

Appreciate all the advice...

Sorry to hear...

Will look into that...

dont worry about it unless you have running problems or have run extremely hi boost, but even then i would not worry too much.
if compression and leak down are good just keep driving it.

sorry, did not mean to worry you. like i said, lots of guys have broken rings and dont know until they pull a piston.

QFT

I think I may have done in a couple of the rings but I firmly believe that some of them had been busted for along time. My car passed a comp/leakdown in the PPI with no issues. The cylinder with the low comp/leakdown we found was the only one which had a compression ring busted.

Bench testing the wastegate showed it was opening around 26psi fwiw.

There were zero issues with my ring lands when I pull the pistons and likewise with the cylinders.

You have nikasil. 930s only had nikasil cylinders, never alusil.

Of course the pistons may be removed from their cylinders for inspection. What is important when re-using parts is to keep each cylinder+piston+pin assembly together, i.e. do not put piston #2 into cylinder #4. Use new pin circlips when reassembling.

Bigger fuel lines would be a plus with your usual bolt ons and a 1bar

You guys are making my day... so far everything is going my way :)

Silly question, maybe...

Any point in lapping the valves? Hate to rebuild the heads as reportedly done by po. I have a couple cylinders I have to look at as there is buildup on the exhaust valves...

Would lapping the valves get the leak down better by 3-4 %? Would a 7% leak down get better? It looks like it's carbon buildup...

I assume lapping the valves doesn't damage anything...

Otherwise, can you just rebuild a couple heads, and leave the others?

Trying really hard not to end up with a complete rebuild...

Any good automotive machine shop has a vacuum tool that measures leakage past the valves. When these are done right, it's 0-1%.
If numbers are higher, and it's got very low miles since last time the heads were off, maybe just lap the valves. Your machine shop would know for certain when the valves are out if they can get by with just lapping, or if cutting is also needed.