J_Kapp

Hi all,

As you can see I am new to rennlist. So far it has been very helpful for me. I got good response on my first post on buying tips. I actually just bought an 86' 951 from a rennlist member. I can't wait to pick it up next week in Mass and drive it home! I'm looking forward to my first speeding ticket.

Anyways to the point of all this. The car I'm getting is basically stock except for and exhaust and a Lindsey boost enhancer. I was on Lindsey's site and they had a mechanical boost control for pretty cheap. I talked to my friend about this and he said that electronic boost control is the way to go. What are the advantages/ disadvantages of both? He also mention that I might want to think about a dual port wastegate. The stock one is single. What does this mean?

The point of all this is that I would like to lower my boost pressure for winter driving (hence the dual port wastegate... I think) and be able to raise it if I do autocross/track days. If I could get some info that would really help a lot

mroberts

Someone's gonna flame you, so I'll tell you nicely. "Search" is your friend. That topic has been beaten to death many, many times.

awilson40

While I like my electronic controller, its a fun gadget to play with.
I noticed very little if any performance benefit over a good MBC.

Mike1982

Yea, I had my car on the dyno before with the Reli-boost (manual boost controller) and it has no spikes and good build of up boost. The curve on the dyno plot is perfect, builds then flat across!

azmi951

What is the lowest pressure you can achieve with the stock WG?
I was on Tials site and the lowest pressure spring for the 38mm WG is .2 bar (I think)

MichelleJD

I believe it's 7-8 psi, but don't quote me.

ninefiveone

I'll add that unless you have two different fuel maps to choose from, it's not a good idea to run two different boost levels. I understand your intent with the lower boost for winter driving but without a second fuel map to choose from, you're have a car running extremely rich at full throttle when running low boost. Depending on how low boost you run, you can be talking about washing down cylinder walls with fuel levels of rich, which is very bad. Engine management on these cars is pretty old and at full throttle, the ecu ignores the O2 sensor and the stock AFM is maxed out anyway so it's reading straight off the map.

Isn't it much simpler to just not press the throttle as hard?

Dr. Dynamics

EBC advantages:
- Some EBCs have an advantage of controling an output for nitrous, water inj, Intercooler sprayer, whatever.
- Various boost settings without popping the hood
- The EBC functions as a gauge
- You can play around with the gate opening pressure and sensitivity according to your drivability
- Safety boost setting,
- Alarms

Disadvantage
PRICE

Remember that if you want to lower boost, the lowest you can go is what the wastegate spring allows you to. Besides, I think there is enough lag for you not to worry, then again, I haven't driven in snow! Congrats on your purchase.

J_Kapp

That is incredibly logical and I will be doing that.

I didn't think about the excess amount of fuel that would be there. I guess I just thought that it would always adjust for the amount of air coming in at all time. I didn't know that.Thanks for the tips.

eniac

I can see with a AFM, since it is maxed easily, why changing boost would need different fuel maps but I don't see where changing boost levels would need a different map wuth a MAF. If you have a good fuel map and a MAF it should keep the same AFR at any boost level that the fuel flow will allow. The O2 is ignored at WOT but the MAF isn't so it should the DME should adjust accordingly.

agree/disagree??

Fen

Not that simple, otherwise there would be no need for fuel maps.

Under boost you want to run a bit rich, off boost you want to lean out a bit to encourage spool-up. You also want to know the load / throttle position as there can be x amount of air passing through the AFM/MAF under multiple conditions. Then you have acceleration enrichment and deceleration enleanment. Lots more to worry about than just how much air the engine is sucking in.

eniac

Well I know the DME takes into account many more variables, such as temp, tps, etc. I'm just saying that I don't see where the amount of boost(within reason) matters since that is directly relevant to the amount of air the turbo is pulling through the MAF. If your fuel map is based on the MAF voltage output it shouldn't matter. All the other variables are already being accounted for and won't change under different boost levels. As long as the bov/recirc. valve vents to back in, so all measured air goes through the engine.

fast951

eniac, with the proper MAF and correct software for it you will be able to modify boost without having to retune AFR. However with higher boost you need higher octane.

eniac

That's what I was thinking. Yes at higher boost timing will be retarded and higher octane gas needed but to change from say 12 psi to 16 psi should not need any fuel software adjustment with a MAF or MAP. An AFM would be different since once that is maxed out is has no way of telling how more much air is going through it.

hally

Hi there Mike,
so you are able to maintain max boost (15psi ? ) to redline with a k26/6 and a MBC ? I am wondering if this is due to the Vitesse MAF, ie were you able to achieve this with the stock AFM?