91 Spirit RT Falls Flat

[mratliff86]

Looking for a little help, the car falls flat above 5 grand. I have tried a different coil and gapped the plugs shorter. It has magnecore 8.5mm wires, less that 3 years old. It runs perfect, pulls hard, it just falls completely on its face above 5 grand. I have a FWD module and it does it on both it and the stock.

[iTurbo]

Sounds like a typical case of the cams being out of time. You'll probably find that one or both cams are advanced a tooth in relation to the crank.

Setting the cam timing on the TIII can be a bit tricky, but you've come to the right place if you decide to do it yourself.

[mratliff86]

Sounds like a typical case of the cams being out of time. You'll probably find that one or both cams are advanced a tooth in relation to the crank.

Setting the cam timing on the TIII can be a bit tricky, but you've come to the right place if you decide to do it yourself.

My brother and I thought that as well and checked it again, he is no stranger to timing these things. I guess we will take another look. Have you experienced this before?

[iTurbo]

Me personally I can't say that I've had that exact problem before. On my red Spirit R/T, I tended to have the opposite problem where it was very soft down low and screamed up to the rev limiter after that. It had aftermarket cams on it though.

I have done several timing belts and have gone through the centerlining procedure with adjustable sprockets, although it's been quite a long time ago I did that. If you have stock cams, you shouldn't need adjustable sprockets and should have no problems revving high without actually centerlining them as long as the belt is installed just right.

edit: forgot to ask, do you have stock or aftermarket exhaust on it?

[mratliff86]

Me personally I can't say that I've had that exact problem before. On my red Spirit R/T, I tended to have the opposite problem where it was very soft down low and screamed up to the rev limiter after that. It had aftermarket cams on it though.

I have done several timing belts and have gone through the centerlining procedure with adjustable sprockets, although it's been quite a long time ago I did that. If you have stock cams, you shouldn't need adjustable sprockets and should have no problems revving high without actually centerlining them as long as the belt is installed just right.

edit: forgot to ask, do you have stock or aftermarket exhaust on it?

I've had both a stock and 3", stock now though. Same problem, with cat or without cat. It is back to stock for time being.

[iTurbo]

How do the spark plugs look? Any indication of rich or lean? Do you run 91 octane at all times or something else?

If you have a scanner like an OTC 4000E, you could check to see if it is pulling a lot of timing out at WOT. I would also pull the valve covers off and take a good look at all the roller rockers to make sure there are no problems there if you haven't checked them in a while.

Also, are you still running stock turbo? There is a slight chance that the air inlet tube between the air box and turbo inlet may be getting sucked shut, choking off flow if the air filter is getting super dirty.

[mratliff86]

How do the spark plugs look? Any indication of rich or lean? Do you run 91 octane at all times or something else?

If you have a scanner like an OTC 4000E, you could check to see if it is pulling a lot of timing out at WOT. I would also pull the valve covers off and take a good look at all the roller rockers to make sure there are no problems there if you haven't checked them in a while.

Also, are you still running stock turbo? There is a slight chance that the air inlet tube between the air box and turbo inlet may be getting sucked shut, choking off flow if the air filter is getting super dirty.

Haven't checked plugs but were replaced in past year. Not rich or lean, 91 minimum.

i can get access to a scanner, I will keep that in mind.

Stock rebuild with quick spool in last year from TU. The air filter has been replaced in past year as well, I will try to run it w/o the airbox hose if everything else checks out.

I appreciate all the feedback.

[2.216VTurbo]

I chased this problem on the Rampage RT for months and months, when it was cold, it was fine, as soon as the motor was at full temp and usually in 3'rd or 4th gear under WOT, it would just stop making power, almost like overboost but not quite. it was the rubber 90degree intake elbow getting soft when hot and vacuuming itself shut when the turbo compressor was pulling lots of air.

[mratliff86]

I chased this problem on the Rampage RT for months and months, when it was cold, it was fine, as soon as the motor was at full temp and usually in 3'rd or 4th gear under WOT, it would just stop making power, almost like overboost but not quite. it was the rubber 90degree intake elbow getting soft when hot and vacuuming itself shut when the turbo compressor was pulling lots of air.

It looks like I have a process, I will pull the airbox/hoses tonight and see if that's it. If not, check plugs again, and if that isn't it check timin and then scanner.

Thanks for all the input, I'll let you know how it goes.

[mratliff86]

Well, pulled the airbox and drove it, that was half the problem. The plugs were kind of hosed, looks like I need to replace those and come up with an intake solution. Any great ideas for crafting an intake?

[2.216VTurbo]

Well, pulled the airbox and drove it, that was half the problem. The plugs were kind of hosed, looks like I need to replace those and come up with an intake solution. Any great ideas for crafting an intake?

You can keep the stock box if you want, just repair/replace that 90 degree rubber intake hose. lotsa aftermarket choices, www.siliconeintakes.com is a good start.

[mratliff86]

You can keep the stock box if you want, just repair/replace that 90 degree rubber intake hose. lotsa aftermarket choices, www.siliconeintakes.com is a good start.

That looks like a great start. I am going to have to think about how to do it since I am about to start collecting pieces for a turbo upgrade.

[iTurbo]

The stock turbo intake hose is actually about 180' bend up to the air box. The turbo inlet side is 2 3/8" and the stock air box is 2 3/4".

+1 on the siliconeintakes.com. In my experience the quality is good and the prices can't be beat. I have no bad things to say about the clamps or silicone I've bought from them. I tend to avoid buying mandrel bends from them though, but only because I don't like shiny stuff.

You'll have to decide if you really want to keep the stock airbox or not. Personally I'm not shooting for the moon as far as HP, so I like to keep stuff stock appearing under the hood.

I would try to find:
2 3/8" to 2 3/4" 90' transition coupler (2 3/8" end attached to turbo, 2 3/4" end pointed up)
2 3/4" '90 coupler (attached to air box)
short section of 2 3/4" aluminum pipe
T-bolt clamps to put it together

The 2 3/8"-to-2 3/4" 90' coupler might be hard to find. You can probably find a 2 1/4-to-2 3/4" '90 coupler, or a 2 1/2-to 2 3/4 90' coupler and make that work though. In the end it could be made to look stock and would be collapse proof.

[DoubleD]

I had the same problem on my R/T with the stock intake on a 50 Trim, I frist found the air filter was too restrictive, swapped to a K and N, then I saw the bendy hose that goes from the air box to the turbo collapsed, it even has a reinforcing wire inside, but the pressure was too high. Lucky the turbo did not suck the wire in, I pulled the stock intake and installed a 3" Cold air intake from a Honda, problem solved.

+1 also for siliconeintakes.com, there couplers and silicone hose is top notch!

[mratliff86]

I had the same problem on my R/T with the stock intake on a 50 Trim, I frist found the air filter was too restrictive, swapped to a K and N, then I saw the bendy hose that goes from the air box to the turbo collapsed, it even has a reinforcing wire inside, but the pressure was too high. Lucky the turbo did not suck the wire in, I pulled the stock intake and installed a 3" Cold air intake from a Honda, problem solved.

+1 also for siliconeintakes.com, there couplers and silicone hose is top notch!

Which CAI and for which Honda? I am thinking that putting together an intake may be the way to go although I do like the stock look.

[DoubleD]

My dad had a bunch of CAI, I had to modify it quite a bit but all it is, is a 3" pipe with a smooth 90 degree bend in it.



This is with my Holset, but I had the same set up on my 50 trim, I just had a smaller elbow. 4" inlet on this turbo, vs 3" on my 50 trim.