87_951_Turbo

Hey guys just got a mbc and i dont know what to set the boost at. I dont want to blow up the engine but would like to know whats safe to run on a stock engine?

I currently have a dual port wastegate, and 3in exhaust from lindsey

Josh B

If you don't have aftermarket chips in the car for higher boost or are running higher octane gas you should really leave it at the stock 11 PSI.

If you were able to monitor knock and A/F ratio and egt and knew that you were safe on all those fronts than I suppose you could turn it up a little more.

choinga

I'm in the same process with my car...

Get the Vitesse AMF chips (John rules...will build a custom map for your car/upgrades and provides several options that you can tweak using the FQS switch on the DME (where the chip goes)). Others have the 951MAX chips (can get them from Lindsey) and have had good results (I actually have a DME/KLR 951MAX chip for sale if you are interested...). Either of these compensate for higher than stock boost by making sure that you have the proper fuel map so you don't run to lean and $%&$ your engine.

Per John - no sense in running past 15PSI with stock injectors and turbo anyway so anything above that is just playing with fire.

From my research on this topic - you want to set the MBC in 3rd or 4th gear - whichever one you spend the most time at and push boost. As you move to higher gears the boost will increase so setting it for 15 in 2nd will get you in the 20PSI range in 4th or 5th which is not good if you aren't chipped (and other stuff) for it. You'll see slightly less than 15PSI in lower gears, but that's to be expected with a MBC - there's no way to force it up 15PSI in every gear with a manual controller. If you want that type of control you'll need to invest in a electronic boost controller.

The stock boost gauge in the dash is worthless, but I've at least been able to note how it correlates with my aftermarket gauge so that I can use it instead of looking down by my radio to monitor boost when I'm driving. With this, I can at least see where I'm at when driving hard so that I don't overboost in higher gears.

You definitely need to run the highest octane gas you can find at the pump - at least 91/93 grade if you plan to push boost up into the ~15PSI range.

If you don't already have an aftermarket boost gauge - get one. At minimum you'll need a narrow band A/F mixture gauge but preferably a wide band - especially if you intend on tweaking and increasing boost. The A/F gauge will tell you what your mixture looks like at boost and if it's not rich then you need to start fixing some stuff.

Do you have a Tial WG by chance - any idea what bar spring is in it??

87_951_Turbo

ok so look to get a set of chips!

i do have an adjustable fuel pressure reg. so i turned that up a bit just to be safe, also i do use 91-93 octane. Ill just leave it on 11psi then.
Not sure on the spring rating, its the lindsey dp wastegate.

what are a good set of chips to get? Theres probably some posts

choinga

I just told you. The consensus is the Vitesse AMF chip (no you don't need the whole board...they run $355 shipped and John creates a map for you for YOUR car and provides a few options based on any upgrades or tweaks you might want to run).

http://www.vitesseracing.com/html/chips.html

Just email John @ John@vitesseracing.com - he's awesome.

Or...the 951MAX chips. You can get them directly from Lindsey:

http://www.lindseyracing.com/LR/Pors...-MAX-CHIP.html

They run $299.

porshhhh951

For outta the box tunning with the stock Motronic Vitesse Racing is the best there is. You will find no one better.

I suggest you drop him a email John@Vitesse.com or visit his website at www.VitesseRacing.com

Charles A. Toupin

What is the target for the air/fuel ratio?

Tx

c.

Josh B

Hopefully some of the more knowledgable folks will chime in here. From what I understand at idle you can safetly run 14.7 and higher - 15.5. Heck sometimes on my car I see 16.5 at idle.

Normal driving off boost you would want to see 14.7.

Then the tricky part. I've heard a couple different opinions on this. Some say that under any boost at all you should see 11.5 +/- .5. Other say that by 6 or 7 lbs of boost you should be under 12.5 and then continue dropping into that 11.5 +/- .5

On an NA car I am not sure what the numbers should be but I think it is 14.7 for normal driving and under load maybe around 13.5 +/- .5.


Hopefully someone will correct me if I am wrong. These numbers are based on partly as well on experience watching a Innovate wideband and then a Zeitronix wideband in my car for about 5k miles. My current compression numbers are about 135 across all four and leak down is less than 7% across all four. I don't monitor knock but I should. I run on pump gas with 3 bar fpr, 55lb injectors and a Vitesse maf and chips at somewhere around 16 or 17lbs of boost with a 60-1 hifi turbo on a #8 hotside.

95ONE

11.8 AFR boost. stay out of the 12's.

xsboost90

i dunno- i hooked my zeitronix up with my car dead stock besides the exhaust and Tial wg and was running 14lbs w/o looking anything but alittle rich...above 15 is only available for a second before boost cut but thats when things started to lean out.

Josh B

Hey Dan - what sort of A/f numbers were you seeing at idle, normal driving and on the boost curve? I am really curious to know what the cars do stock. Also - did you have an EGT probe in?

mzman

Ya, I have been told 13.3-13.5 with any kind of boost, then shoot for 11.5-11.8 at full boost. Then 14.7 off boost running around town.

xsboost90

if my computer hadnt crashed last year i would have a file from the ZT2 but its gone. 14.7 stock at idle and into the lower 13's mostly but once you got to 15psi it shot up quickly. Stay 14 or below.

brrgrr

Around town your factory O2 sensor is going to control the AFR to 14.7. Once you put your foot into it the car will stop using the O2 and start using the fuel map -- I've been told the target AFR should be Mid 12's from 3000 to 4000 rpm, low 12's from 4000 rpm to 5000 rpm, high 11's from 5000 rpm up to redline.

Oh - safe boost levels - depends on who you ask and what kind of set up they have ! If you have the injectors and map to maintain a good AFR, 17 lbs seems to be a max number with the stock head..... after that valve float can occur and you should go to a solid lifter head, so I've heard.

Charles A. Toupin

Thanks guys!

c.