Removing AOS heat shield.

Champagne · 12-16-2008, 04:41 PM

I unbolted the AOS heat shield but have had no luck getting it out. I can wiggle it pretty good.
Do I need to remove the down pipe to remove the AOS shield? TIA

nize · nize's Garage

there is one bolt that attaches the downpipe bracket flange to the motor, you must remove that bolt to remove the heat shield for the AOS. be warned, once you remove that bolt you will most likely never get it back in without removing the motor. it looks easy but it's notoriously difficult to replace that bolt because three different things must line up in unison for the bolt to seat properly, and you only have two hands.

Techno Duck · Techno Duck's Garage

Ive read a few old posts over on RL that say using a stud in place of the bolt makes life alot easier. I am going to try that way when i put my turbo back in hopefully sometime next week... if its still too much trouble im just going to leave it out...again

.

nize · nize's Garage

i thought about leaving that bolt off, until i realized if you leave the bolt out, the entire weight of the exhaust system including the downpipe will be hanging off the turbo hotside, which is supported only by the two flimsy turbo mount bolts. i couldn't forgive myself if that stress and vibration caused the turbo to warp and fail.

trivgar · 12-31-2008, 07:23 AM

Yep. Left mine out.

Techno Duck · Techno Duck's Garage

Put my turbo in tonight, the downpipe bolt was easy as heck. I did try using a cut down exhaust stud which ended up still being too long.. so rather than bother with cutting it down more (and probably cutting it too short) i tried a bolt. The bolt threaded right in with me reaching up from below the car. Go figure..

Its not tightened all the way down yet, i just bought a 13mm flex socket. The universal flex with a 13mm socket was way to long to fit into that spot.

trivgar · 01-05-2009, 12:00 AM

Crazy. Almost makes me wonder if I should get under my car and try and slap a bolt in there. I only tried from the top for some reason.

Techno Duck · Techno Duck's Garage

The bolt is a M8x25. It may have helped that i had the heatshield and intake manifold support tightened down with that front bolt and the stud in place so it was all lined up already. Beats me!

wild man · 03-03-2010, 07:52 AM

Quote:

Originally Posted by Techno Duck

The bolt is a M8x25. It may have helped that i had the heatshield and intake manifold support tightened down with that front bolt and the stud in place so it was all lined up already. Beats me!

Why was the pic that you posted moved or deleted?

Do you sleep a little better now, knowing that the pipe is secure, after letting it "float" for so long?

I am now considering a 3" downpipe as my "final" upgrade, after the K27, which was my previous final upgrade - does it ever stop? But it does seem to make sense, to complement the k27, though. It should reduce the boost increase that would be required to reach 400hp, right? Either way, I'm definitely not going over 25psi, no matter what. Any opinions on whether or not a k27, 3" DP, and 5psi will take me to 400, from current 335-340 @ 20psi? And how many hp would I loose if not upgrade DP to 3"? (Anyone have 1 for sale?)

I was getting a little off-topic there, but my question is that if all of the 3" DP options do not use said bolt for support, then what IS supporting them, other than the TC itself? The 3 inchers would have to weigh more than the stock 2.5's, right?

nize · nize's Garage

nothing supports the 3" aftermarket down pipes, all of the weight is on the turbo itself.

i've been considering the 3" downpipe as well, but could not find any back-to-back dyno comparisons between the stock vs. 3" downpipe, so i opted to stay with the stock one for now.

if you look at the turbo hotside outlet, it's way smaller than 3".

wild man · 10:24 AM

Ouch, that feels like a lot of weight to have to carry. But I just got to thinking, that due to space considerations, the 3" might NOT be double-walled. If that is the case, it probably IS lighter. I would have thought YOU would already have the 3" DP mod.

As far as dyno results go, someone who did do it claimed +15hp with 3" DP, and rest of exhaust stock. Then got an additional +20hp, after going 3" for the rest of exhaust. But my intuition tells me that he would have gotten the same results (15 first, then 20 more) if he did the mods in reverse order. Since I already have 3" exhaust, I'm thinking I could gain 20hp if I go with a 3" DP. Either way, it seems that 15 would be the MINIMUM increase with 3" DP. And if I may "extrapolate" a little bit, I think that with a K27 @ 20 or 25 psi, the absolute minimum qain would have to be in the neighborhood of 20 to 25 horse power.

running_cold924 · running_cold924's Garage

i don't think they do double-wall downpipes much in the aftermarket, especially for a 951 where space is sooooo limited. i'm keeping my stock one but have thought of heat wrap or a thermal coating for it for heat. I also made sure the inside wasn't collapsed either!! but then again, i don't believe it has been tracked, just driven spiritedly.

my goal is to get that bolt back in for mine

nize · nize's Garage

Quote:

Originally Posted by wild man

As far as dyno results go, someone who did do it claimed +15hp with 3" DP, and rest of exhaust stock. Then got an additional +20hp, after going 3" for the rest of exhaust. But my intuition tells me that he would have gotten the same results (15 first, then 20 more) if he did the mods in reverse order. Since I already have 3" exhaust, I'm thinking I could gain 20hp if I go with a 3" DP. Either way, it seems that 15 would be the MINIMUM increase with 3" DP. And if I may "extrapolate" a little bit, I think that with a K27 @ 20 or 25 psi, the absolute minimum qain would have to be in the neighborhood of 20 to 25 horse power.

where's the dyno comparison? i have yet to see any actual proof that a 3" downpipe makes more HP with the stock 2.5" turbo outlet.

i can see if you went with an aftermarket 3" turbo outlet it would remove a restriction, but on the stock 951 the restriction is the turbo outlet itself, which is 2.5".

again, this is all speculation. i was going to do a before/after dyno comparison myself but got too busy with other, already proven projects.

running_cold924 · running_cold924's Garage

may have more of a benefit/gain by using that $300 for the intercooler instead... just my $.02

wild man · 03-03-2010, 08:30 PM

I haven't seen the dyno comparisons. I'm just going by the guy's word. What he said does seem entirely plausible to me though. And I can pretty much guaranty that slapping a 3" DP onto a turbo with a 2.5" outlet is definitely going to make a noticeable improvement. Doing so on my 88 t-bird turbocoupe dropped the boost onset point by a good 150rpm, while quickening spool-up by a very noticeable amount. And that was with a very primitive DP, that I constructed myself, using only straight pieces of pipe. But there is absolutely no doubt in my mind, regarding the difference that it made. It was just like switching to a turbo that spooled sooner and more quickly.

wild man · 05:47 PM

I ended up sticking with stock also, on the outlet pipe (and DP). But internally it is modified. I have ported out both ends to there the welds are flush. That is 2.5" (1ft) coming off of a 2.25" #8 turbine outlet. After that, it goes to 2.75" (3ft) on the trip down. The stock DP has "modified internal passages", then it is 3" the rest of the way. The waste pipe does NOT dump back into the exhaust system. I don't think you could do too much better than that for exhaust. It's still not ready for start-up yet, but close.

EDIT: I have the pics, will get them up soon. You can see the internal modifications clearly.