Huntley Turbo-2 and MAF-4 Installation
(this page copied from Bill Shook's website at
http://members.aol.com/skydiven/porsche951.html)
Ok, well..it's been in my car for about 3 weeks now so I guess it's time
for me to spill the beans. About 9 weeks ago, Joe Obrien and I decided that
it was time for us to install the Huntley stage 2 turbo and stage 4 MAF
in our cars. Mine is a street/track car and Joe's is a track/street car.
The differences are what you would expect, mine is nice and comfy and like
the factory shipped it with a few more performance goodies. Joe's is like
the factory wished they could ship it, caged and stripped and 320 pounds
lighter than mine. Here's the Huntley experience in its entirety, some good,
some bad...like life, nothing is ever perfect. First let me say that although
I refer to using Derrek's name in vain several times here, that's all in
fun and I have to respect Derrek alot for making a system like this work.
This write up will help others who want to install the Huntley set up by
describing every problem I encountered. It is certainly not meant as a complaint
for the difficulties, just an overview to make those difficulties fewer
for those who go the same route.
I called and spoke to Derrek. Joe and I agreed to buy two stage 2 turbo's,
two stage 2 MAF's, two adjustable Fuel Pressure Regulators, and one stage
3 MAF (for a customer). Derrek told me the turbo's were in stock and ready
to ship and we told him Joe would be in California next week and would pick
them up at that time. As it turns out the turbos were actually cores in
stock and were not done the following week, nor were they done the week
after that. In fact, the credit card bill for ordering them showed up nearly
before the actual equipment did. I understand the turbo's are very new and
his machinist that actually prepares them took longer than expected which
caused Derrek to break a few delivery promises...it happens. Noone was happy
about this turn of events, believe me.
Turbo: Well the intake on this thing is freaking humongous. I mean REALLY
big. The center section is Garrett, the cold section is Garrett, the hot
section appears like it's KKK, but has no marking to say such. It has a
hole in the cold side that you must buy a plug for (1/8" pipe thread)
and doesn't come with any studs in it. So you can enjoy the removal of the
studs in your current turbo as much as I did. Keep in mind they've been
heated to glowing red thousands of times since installed so double nutting
them isn't the easy chore you hope it will be. I may have used Derrek's
name in vain a couple times at this point.
Let me save you the two hours that Joe and I spent by telling you the hot
and cold sections are both indexed wrong. The cold was obvious because it
was pointing exactly the wrong way but the hot section was only off about
20 degrees so it was another full turbo install before we figured out the
hot side was also indexed wrong and wasn't going to line up with the exhaust.
(getting the idea of how many times we had to fight those dame Allen heads
that hold the turbo on?). Ok, so the trick is to leave all index bolts loose
(you have no idea how much time I just saved you, should you decide to install
one of these), install the turbo so that it actually lines up with everything
(well almost everything, we'll get to that in a minute) and tighten a couple
of the index bolts on both the hot and cold side...remove it all again,
tighten all of the index bolts and then intall the turbo for real. Now,
about that problem I alluded to earlier. The Garrett center section is a
full 1/4 " narrower than the KKK it replaced. What does that mean?
It means the bolt that goes through the down pipe coming off the turbo won't
hit the mounting boss on the block. This all seems so easy to type, but
figuring out what the hell was wrong took a lot longer and again Derrek's
name was used in vain many times. You can't see up in there so you're feeling
around, trying to figure out why that bolt isn't threading in. A mirror
would have told us, but neither Joe nor I carry a pocket mirror :)
Ok, we call Derrek and tell him that the downpipe doesn't line up. He say's
'Oh, yeah that's why we leave that bolt out'. Alright, I'm a fairly open
to suggestion guy but leaving the weight of the front half of the exhaust
hanging from two little allen headed turbo bolts with a lever the size of
the downpipe to pull from just doesn't make any sense at all to me. I think
the $1550 turbo should have an adapter with it that moves the downpipe back
far enough to actually 'bolt in'. But, alas... I slotted the hole in the
down pipe and put that bolt in. I just sleep better that way. I mentioned
that to a local Porsche shop whose mechaincs used to wrench for the factory
951 effort and their response was 'Leave that bolt OUT?, uh...I think not'.
Me too, but I admit I may be wrong. After a week in the car, the downpipe
bolt has vibrated out anyway...so per Derrek, it stays out. He said it wouldn't
work with the bolt, and he has also since then used the I told you so phrase.
:) Oh well, I tried...and it still makes me nervous hanging that downpipe
off with no support....but if the manufacturer says to do it.... The overall
impression of the installation is that on a scale of 1 to 10, with changing
an air filter being a 1 and changing a 951 clutch being a 10....the turbo
install is a 9. Maybe a bit easier now since I've laid it all out for you.
So, now the turbo is in, for better or worse and it's time to look it over.
What is this? The turbo outlet is a good inch beneath the top of the alternator.
Hmm, another phone call. 'That's normal, the MAF rubber adaptor will make
an 'S' shape when you shove the MAF manifold on it and it will work.' Ok,
well it does. It works but there is a worry in my mind. Now the rubber sits
right on the metal corner of the alternator. I'm thinking wear through here,
but have no idea if it actually will, I hope not. The K-27 upgrade also
does the same thing as far as lining up beneath the alternator. So, if you
want a bigger turbo, it can't be avoided I guess.
I'll save you another hour now. You WILL have to cut those pretty Purisil
hoses in order to make the stage 4 MAF fit (not the case with the stage
3) and the hood close. The MAF unit, with hoses intact is a good 1/2"
too long. After much use of Derrek's name in vain again, I broke out the
razor knife and 20 minutes later it was in. The manifold actually sits up
inside the MAF sensor by a little, but it's in and the hood finally closes,
though it does hit the filter a little and I did have to crush the filter
a bit to clear the rotating headlight. It is likely that further cutting
on the hoses would move the filter far enough back to prevent any contact
with the hood, but I didn't feel it was necessary so I didn't do it. Also,
Derrek informed me later that the hoses are left long intentionally....better
long, than short. True, and I'm sure the directions will mention this soon.
Alright, now you want to know how it performs. Well, that is where this
little novel turns into good news. First gear builds 16 psi of boost, where
the Turbo S used to max at 13 psi of boost. Second gear builds 18 psi of
boost where it used to max at 15 psi. This all means that 1st gear lights
up the 9" rear tires VERY VERY easily and second gear will light up
at will as well. Very fun. In 3rd it hit's 20 psi but won't hold it past
5000 rpms. 4th is the same, and drops to 17 or 18 psi by redline. I must
admit I expected this setup to be SCARY fast, and it doesn't scare me...but
there is no way to hide the numbers. A dyno run showed 344 hp and 342 lbs
of torque at the wheels. That is a LOT of horsepower. I didn't beleive it
when it put that out on the dyno, so I made them run it again - same result.
At the racetrack, my car fealt wonderfully powerful coming off corners and
was very fast down the straights. I ran two seconds under my best previous
time at Roebling Road (1:26.1). Not bad at all in a street car with full
interior and stock wheels. The turbo does appear to suffer from the standard
Hybrid curse, it smokes. I get comments on the oil smoke out of my exhaust
when I shift, but all I can say is 'Yeah, but you were BEHIND me when you
saw it, were you not?' Full boost is obtained at about 4000 rpms in 4th.
I ran the dyno run at 20 psi of boost, which is a LOT, but it seems to run
just fine at that so far. I do intend to drop it back to 18 psi and leave
it there. At the track I blow flames out the exhaust when I lift throttle
and on the street there is the occasional fire explosion out the back as
well.
In conclusion I guess I'll sum up the positives and negatives.
Positives: 344 hp, 342 lbs torque.
Negatives: install is no picnic, downpipe bolt doesn't line up, smokes,
pricetag.
Draw your own conclusions, make your own decisions, take a look at the dyno
sheet below. I think I'll keep mine.
