streckfu's

How's your AFR?

JustinL

This is the key. 14psi on one turbo can have a different ammount of O2 than 14psi on a more or less efficient turbo. With different efficiency of the compressor side, you would need more or less fueling depending on how much the air is being heated.

A change of the turbine side would change the VE of the engine and may also neccesitate change in fueling.

The degree to which fueling requirements change with different turbines and compressors I'm not sure of. To have everything running perfectly, you would need propperly matched chips and the ability to fine tune.

Porschefile

Are you guys blind? Did you not read what my post said? WITHIN THE LIMITS OF THE FUEL SYSTEM!!!! If he's still on a stock fuel system then he is going to have to be MUCH more careful! He could still use the K27, though I would highly recommend running less boost on a stock fuel system (lets say ~8psi to be safe). The most important thing here is what chips he has and how they are tuned. If the fuel maps were tuned pretty crappy to begin with, then a larger turbo is only going to amplify this. A wideband or baseline dyno at lower boost would really help to verify what the a/f's look like. I, for example, upgraded to 55# injectors and a 3 bar fpr with my VR maf chips. I'm still on the stock k26/6. Since I have decent chips and the proper fuel system, I could throw on a 27/6 or even a 27/8 and the chips would still function fine. The 27/8 spools up a bit later, so my a/f's would be a little rich, too early in the rpm. This will hurt spool and performance a bit, but not to the tune of 50rwhp or anything. For optimal power, yes I would need to fine tune the maps, though in my case a piggy back would work just fine. Do you guys see what I'm getting at? Yes it IS possible to do these things, however you are going to be restricted by fuel limitations and the quality of the tune on your chips. It's not going to be optimal but it WILL work provided you don't exceed these limitations.

streckfu's

Then what the hell is the point? That's like Dragaliscious telling people to slap whatever width of wheel that will physically fit and 'see' what happens.

Good advice would be to tell him to save the money and wait until he can everything at once, if funds are an issue. Good advice would be telling him that he needs to adjust fuel on a dyno before boosting.

REALLY BAD FUC*ING advice is telling him it's going to be OK when he's mostly likely going to be running lean with the increased airflow. Even worse advice is stating that a car tuned optimally for a K26 will need no changes when installing a larger turbo.

And for the last time, a MAF cannot adjust fuel. PERIOD.

All of you have admitted that it's not a good tune so why tell him he can IF he sets all these limits. That's bull**** and horrible advice. Shame on all of you!

Peace.

pk951

Have a good day.

>

Porschefile

The point is IPSC never posted his mod list, so there's no way of knowing if he has the proper mods, fuel system, etc to handle the turbo. I'm speaking theoretically, and it's up to him to decide what he feels is safe. I'm simply stating what IS possible if he does in fact already have an upgraded fuel system.

No argument there. If you look at the context of my posts in this thread, you will see that I am emphasizing the fuel issue. I personally don't recommend doing any of this without at least upgrading your injectors and fpr, which of course requires a tuned chip. This is the exact reason I upgraded these things, even on my stock turbo. This is a good investment for anyone that plans on doing more than a couple of bolt-on mods. On top of that, your injectors will be at a lower duty cycle and less stressed.

I never said it would be ok for IPSC's setup, and I never said changes would not need to be made. Yes you will need a retune going with a larger turbo if you want it to operate 100% efficiently. IPSC never posted his mod list so there is no way of knowing.


Yes the maf, afm, map etc do not adjust fuel themselves. They simply provide the signal so the DME can determine how to adjust fuel. If you already have upgraded injectors and a fpr, then you CAN install a larger than stock turbo and the DME will "maintain" the same a/f's as before due to the airflow signal from the maf. There ARE limitations to this. If you have the proper fuel system, even though you might be producing increased hp from the larger turbo the DME will still maitain the a/f's up to the point where the fuel system is no longer capable of handling the power level. The a/f curve might not be optimal any longer, depending on how different the new compressor is. Maf's enable the DME to adjust for changes in airflow, as long as it is within the maf's operating range.


On a final note, to answer IPSC's question, you really need to upgrade your fuel system if you don't want to risk damaging your motor. This of course includes a higher pressure fpr and larger injectors which will need a retune to work properly. Yes, if you really wanted to, you could probably get away with running low boost (below 10psi), but it's really a matter of what you are willing to risk and how well your chips are tuned.

Someone sell me a 27/8 so I can throw it on and prove my point!

streckfu's

We agree,then.

I was taking issue, mostly, with Drft's posts that he can just install the k27 and call it good. There is a right and wrong way to do something. That is the wrong way.

AL951

Hi,

I don't know my AFR, but like I said before the car runs and performs just find. I also get very little Knock but then the computer steps in and it goes away. so I gess my AFR is ok or close enogh.I am very happy with the change.


Regards,
AL

streckfu's

Your AFR is NOT 'close enough' if you're getting knock. You really need to check what's going before something breaks...something expensive. Knock is BAD.

I can't believe some of the posts lately.....

AL951

Well Daniel,

to much knock is very bad for any engine. But alittle will not damage the engine. And this is what i mean by little. as you get hard on the go pedal and the turbo spools up and you are making good boost at hi revs, sometimes (not always) you can here alittle knock like for like half a second or less, the it goes away like it suppost to do. their is no problem with this. So if the KLR is working correctly it should do this. If i was getting knock every time I would accelerated, then I would be very, very worry.

regards,
AL

lart951

Btw, I have dibs in your car.

AL951

I'm sorry what is "dibs" Lart?

Regards,
AL

IPSC

WOW I did not think that THIS was going to be such a hot topic and sorry for not paying attention to it sooner. Been Busy getting ready for the first DE.

Ok Here is what lead to my question. My 89 951 came with an Autothority MAF, a set of Autothority chips and jetted banjo bolt, a k27/6 AND the best part... a blown head gasket (more on the blown head gasket in a second).

I was told this was all part of a Powerhause "kit." I have been doing some digging and it seems that the chips are (according to the one person who would talk to me at Autothority) for a k26 set up. I don't know if that was a mistake in the packaging or what. Talking to the people at Autothority is a project in and of itself. They almost hung up on me when they found out I was not the original purchaser of the chips. In fact I was asked repeatedly if I had bought them off of ebay. When I replied that I had not, about three sentences later another round of "where did you get them" was played out.

Anyway I am wondering if the mis-match of chips to the turbo could have contributed to the blown head gasket as I do NOT want to go through that again.

At the moment I am running Guru chips (that I just found out the other day) are mapped for a K26... now the fuel curve is so rich it isn't even funny so I am not worried about running it lean. I am in the process of replacing the chips YET again. I do have an Adjustable FPR and I have plumbed in a boost gauge. I have bypassed the cycling valve with a MBC. I have add a Tail wastegate and I am running no more than 15 PSI. A Piggy back / wideband is next on the buy list.

So thanks for the HUGELY informative thread, I do appreciate everyones input.

IPSC

streckfu's

Once you get the WB/PB, you will have the flexibility to tune at will; even using hte old APE chips.
It appears your PO added the K27 without new chips and blew the HG....

lart951

It means that after you are done blowing your engine, I will make the first offer to buy the non-running car from you.