Boost

Uberlegen · 03-16-2005, 01:36 AM

Hey guy's new to the board just got an 86 Turbo.. Wondering what the maximum amount of boost that i can put out with a stock setup is?

Lawrence Coppari · 03-16-2005, 02:44 AM

Factory setting is 1.8 bar absolute pressure. That is about 12 psi above atmospheric.

Uberlegen · 03-16-2005, 03:08 AM

hm.. So the maximum boost it could put out is 12psi or is that what it comes with from the factory? Sorry still learning the terminology

Lawrence Coppari · 03-16-2005, 04:55 AM

It will put out more. Factory setting limits it to 12. Don't know how exactly much it'll put out. You might want to change the head gasket if you go with higher boost.

Uberlegen · 03-16-2005, 05:45 AM

Yea, i was thinking the same thing, greatly appericiate the response.. Trying to read up to learn as much as i can about 944 turbo's

Lawrence Coppari · 03-16-2005, 09:24 AM

I bought mine in 1996 with 89K on it. In January 1997 I put a K27 and a MAF on it plus higher fuel pressure. In 1998 it got an extrude honed intake and ported o-ringed head and different gasket. In 2000 it got a reamed throttle body and bigger, straighter boost tubes. It now has 153K on it and about 60 track events. It burns some oil and leaks some oil but other than that it is fine. I run 1.1 bar.

DannoXYZ · 03-16-2005, 01:52 PM

Boost is not the limitation. It's that the fuel & ignition programming has to be matched to the actual air-flow volume you have. I've run 25psi with no problems on the stock motor and turbo with water-injection. Fuel & ignition was programmed to match those conditions. An aftermarket EFI system is the most flexible route there and the system I was using also controls nitrous and water injection as well. It then increases fuel to match the volume of nitrous injected and subtracts fuel based upon water.

Uberlegen · 03-16-2005, 02:00 PM

Danno, question i was under the impression that it's not wise to use nitrous with a turbo'd car 3 of my friends have GTI 1.8t's and when i mentioned it they said it would be a great way of blowing your engine.. Curious about that one

DannoXYZ · 03-16-2005, 02:08 PM

It has to do with fuel delivery and ignition timing and combustion pressures. I have two separate ignition maps for use with nitrous on and off. WIth nitrous ON, I use about 7-degrees of ignition retard compared to the standard maps. Water injection allows me to restore about 3-degrees of ignitoin. So there are three separate maps that are overlaid on top of each other, a 25psi ignition map, then an adjustment for nitrous and an adjustment for water-injection.

Then fuel must also be increased to match the flow of nitrous as well. The old and crude hot-rod method of injecting fuel to match is having an extra injector with the nitrous nozzle and dumping an appropriate amount of fuel to match. Since my nitrous is injected with 3D mapping based upon LOADxRPM, the flow is variable. Thus the fuel increase to match is also variable.

There's really no black & white, yes/no, all-or-nothing type of things with anything in life. It comes down to "what ifs" and "what it takes" to get things to work, and work well and safely. I find going back in history and researching the kinds of programming needed to generate 1300bhp+ from the 1.5L turbo F1 cars of the mid-80s gives you a lot of insight. Some of these details are coverd in the "Fuel FAQ" online. I've got a link to them on my 951 RacerX website.

Uberlegen · 03-16-2005, 03:44 PM

Hmm interesting.. So if i were to upgrade to a larger turbo.. would i be able to run at a constant higher boost high 20's or is that pushing my luck?... don't want to blow the engine

.. Friend with the GTI 1.8t is running 20 pounds or so.

Evan70 · 03-17-2005, 08:30 AM

On a stock 951, the max most experts would recommend is 18psi. Of course, that's assuming that everything is in good condition on the car. These cars are now getting fairly old, and many of them are still running the original headgasket. 15-18psi on an original stock headgasket will most likely equal a blown headgasket very quickly (ask me how I know).

murn · 04-21-2005, 03:25 PM

Just want to make sure I understand the setup correctly Danno. I have installed an aftermarket gauge on my car because I didn't have faith in the original gauge. I hit 15-18 psi on aftermarket gauge but the stock gauge barely breaks 1 bar. If I'm reading the other comments correctly I should be able to make 1.8 bar max.

I have a Lindsey manual wastegate setup and a Guru chip that is giving me the 15-18 psi, on the aftermarket gauge. Before that upgrade the stock gauge was only giving me max of 0.8 bar. Is my setup giving me all I should be getting? Or do I have another problem.

Just trying to sort out all the lingo.

Evan70 · 04-21-2005, 04:48 PM

The stock gauge will not go past 1bar, that's why it's very important to have an aftermarket gauge if you are going to run aftermarket chips.

Porsche-O-Phile · Porsche-O-Phile's Garage

More correctly, you only need an aftermarket gauge only if you're running higher than 14.5 psi (1 bar) of boost AND a manual controller. Personally I'd get a good electronic boost controller; this will display boost level (hopefully it's what you set it at!) and other information. This way you can avoid the redundancy of having two gauges in the car telling you the same information (which admittedly is kind of stupid). Aftermarket chips alone will not raise boost level necessarily.