Paul968

porshhhh951 How long have you been running that level of boost???

I also seem to be running that level of boost...... I have been running this level for about 2 months or so.

As I mentioned above..... my factory boost gauge has not worked since I bought the car (6-7 months ago) and I just this weekend installed a new VDO gauge. Thought I better see what was going on!!!

This is when I found out I was getting 20lbs boost in 4th and 5th..... and it does not let up or bleed of all the way up the RPM.

I am running a higher fuel pressure regulator and a set of 55lb injectors.
This uses a ballast resistor and the DME switch to retard the pulse flow on the injectors. This allows me to use these injectors a lower duty cycle as I dont need all that flow with the level of mods I have right now.

My question is...... can the chip or resistor or something else for that matter, detect a situation whereby the injectors/fuel rate need to flow a little harder if necessary?
Ie..... if the resistor and chip is retarding my injectors flow rate to 38lbs for example, can this level be automatically increased if needed. So if my situation demanded 50lbs for example, would the injectors be allowed to flow that??? once the demand backs off, the level of rate will return to the set/limited level created by the chips and resistor.

Hope this makes sense.

If this is true, a higher level of boost would not cause detonation as the air/fuel mixture would be somewhat matched.

Any ideas?????

Duke

The ballast resistors don't do anything except keeping the DME a bit cooler so just ignore them.

The DME switch is used to retard timing a bit, it has nothing to do with the injectors. Or do you run the Guru chips? In that case, the DME switch is used for different injector sizes.

Your injector flow rate will not be changed automatically.
The injector pulses is set by the chip based on load and rpm.

However, since the fuel pressure rises along with boost level, more fuel is supplied on higher boost levels. But this doesn't do much!

Paul968

Yes, I have the Guru chip kit.

So 16-17 in 1,2,3 and 20 in 4,5 is too high......... this is basically what is comes down to.

I should maybe back off my relia-boost to lower boost levels.

What is my alternative??? Do I have any???

Assuming the right level of fuel can be provided to match the air flow/pressure created by the boost, then detention should not happen, correct???

Also what about air density and oxygen richness??? IE..... the intercooler??? If the intercooler keeps the compressed air from heating up under expansion/forced flow, then no hot spots should occur........ which will prevent detonation.

Surly things can be done to safely squeeze a few more pounds boost pressure into the system.

Any ideas????

Duke

20 psi is a bit high, even if you got the A/F values spot on!
I would not run 20psi unless you have a seriously modded engine with A/F and timing control, datalogging, WBo2, EGT etc

Sami951

Yeah, at some point the pressure (boost + engine compression) just gets too high and you will get knocking, no matter how good the A/F ratios are... esp. if you're still running the stock turbo, the K26 is just too small for flowing that much air, so it's working way beyond it's efficiency range -> heats the intake air a lot more than it should, hot air + lots of boost = detonation...

However depending on the engine and turbocharger, 20psi isn't necessarily too much If I've understood correctly, those Cosworth-built Ford Sierra/Escort (did you ever have these in the states?) engines can run insane boost, 30psi or so is not unheard of ... sick ...

Paul968

I am not sure they came to the USA.... However, I know all about them as I am English and moved to the USA.

This is my point.... I continually see cars, somewhat stock, push higher levels of boost.

I wonder what the difference is.....

Cool fact for ya...... the current Ford Focus 2ltr engine produces 310 hp, which I know is not that spectacular but it produces over 800lbs torque!!!! That's some serious accelerating capability.

I wonder how they get such levels of torque without so much HP.

So if this is possible with a Ford.... I am sure Porsche can do just as well if not better.

Duke

Yeah some cars out there run simply insane boost levels by 951-means!
The cossie 4 cyl. and audi 5-cyl usally run at least 1,7 bar when highly modified! Often 2,0+ bar on some occations (like street/strip-race).

But the cossies have lower CR than we, and combustion chamber design is very very important to prevent pining.
The whole thing with race gas don't appeal at all to me.

However, I think most 951-users are a bit conservative regarding the intercoolers. I mean, look at other modified cars running high boost. For instance the cossies as we've talked about. They alla have the RS500 replika FMIC that's big like a house! No.. more like a skyscraper!

Duke

I don't want to get offtopic, but take a look at this E30 Turbo... sweeeeeet!
Note the rather large intercooler!!!

Paul968

Damm...... that's a BAD puppy.

I love that style and vintage BMW..........

One thing that just occurred to me...... UK and Europe's octane levels are a lot higher than the USA. The gas is poor over here and maybe that's why knocking seems to be more of an issue.

Plus in the USA there is more potential for back pressure, which ultimately causes more heat, because of the extra emission devises on US cars.... ie cats etc.

I still cant not understand why if the right fuel level, plus cold intercooled air was produced, the boost level could not be slightly raised.

I don't mean 40lbs or something crazy but more like 20-24 lbs boost.

Does any one have a 450+ hp car??? if so what fuel pressure, injector size, intercooler and boost level are you running???

'86 944 turbo

that BMW is sweet. I wonder how fast it is?

Duke

That BMW is FAST... I think at max boost with race gas it produced something around 900 hp and 1200+ nm!!

Paul968

Holly Crap!!!!!

Now how come that can be achieved with a BMW but not a 951??? Or can it. I guess with money anything can be done.... right!

'86 944 turbo

thats crazy fast. I wonder why our cars can't do that.

Duke

Here's some specs:

The amazing thing is that it produces 720 hp 950nm on pump gas at 1.1 bar!
On race fuel: 875 hp 1263 nm at 1.65 bar.

One thing you got to keep in mind here is displacement. This engine is based on a 3.8 liter M5 engine.

So 720 hp at 1.1 bar on pump gas equals 472 hp on a 2,5 liter engine.
That's about what TonyG's 2,5 produces at the same boost level.