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Old 04-27-2003, 07:19 PM   #1
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Unhappy Tunning issue with MR12 turbo and RD turbo pipe

I realy have some tunning issues with the MR12 turbo after I changed the REX pipe (engine, pipe and manifold came with MTX3) and manifold with a two piece RD turbo pipe. I use a #5 turbo plug that came with the engine and 30% trinity monster horsepower fuel, now the problem is that the engine idles higher and overheats much quicker when I swaped the pipes and left the previous carb settings. I tried the following:

- Switch to a #6 turbo plug
- Set the low end needle to 1 turn
- Set idle opening in the carb to the thickness of a paper
- Set top end to 2 1/2 turns
- Change manifold to the stock one
- Middle needle flush

These changes helped but what I noticed is the engine runs hot not overheats (230 compared to 200 with REX pipe), doesn't have the torque and accelleration as it did with the other pipe, have to really step on the gas at 1/2 throttle (tap on the gas with the REX and the MTX3 takes off) to get moving (power comes in at higher rpm, but makes engine hotter). Tried leaning the bottom end to 3/4 turn instead of 1 (GOOD: accelleration improved BAD: engine stalls after getting of the gas and idles high and stalls).

My questions are:
1)Is the REX a low end pipe?
2)Do I need to change the plug (hotter or colder) when using 30%?
3)Are the carb setting ok?
4)Is this normal when running a high end turbo pipe (More HP at High RPM with the expense of Low end torque at Low RPM)?

I was wondering if I wasted my money on this pipe and kept everything stock but any tips or tunning suggestions are very appreciated. I might sell this pipe if nothing else improves, if so, I practice at Crystal Park every other Sat. in the afternoon, I run an MTX3 with a bright orange and blue Opel Astra body.
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Old 04-27-2003, 09:33 PM   #2
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1.) I really don't know if the rex pipe is for low end or high end. I drove someones elses car with it on a MT-12 and it seemed to give better midrange power, so I'm just going to guess it;s in between.

2.) When you run high nitro % you usually need to run a bit colder glow plug. When you use a hot glow plug with high nitro it tend to ignite a bit to early and fast. When you use a colder plug you can time it to ignite at Top dead center where it is compressing the air as much as possible, and get maximum power.

3.) Not knowing what your current carb settings are, I can;t really help you. Just to let you know, 200 degrees is fairly cold. My MR-12 non turbo runs about 250-280. these motors can take up to around 290 FOR A SHORT PERIOD OF TIME!

4.) The turbo pipes from what I've heard are for very large tracks where low end torque is not much of a nescesity. It is made to get the most HP from a .12 engine and that usually come at high rpm. So they make it a very smooth non punchy pipe. They make it the regular roar legal. pipe from RD logics has much more low end power. I have one in my car right now and it performs awesome.
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Old 04-27-2003, 10:03 PM   #3
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Quote:
Originally posted by Sushi Boy

4.) The turbo pipes from what I've heard are for very large tracks where low end torque is not much of a nescesity. It is made to get the most HP from a .12 engine and that usually come at high rpm. So they make it a very smooth non punchy pipe. They make it the regular roar legal. pipe from RD logics has much more low end power. I have one in my car right now and it performs awesome.
are rdlogics turbo legal pipes just for modified engines coz I want to putmy non-turbo non-mod MT12 or os12tr on it?
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Old 04-27-2003, 10:50 PM   #4
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No, I don't think so. "Turbo" is just a name, thats all. They giev really good top end power but suffer at low end. Very smooth from what I've heard though.
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Old 04-27-2003, 11:10 PM   #5
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Also, for 30% you may want to consider installing an extra head shim to help combat detonation.
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Old 04-27-2003, 11:13 PM   #6
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Quote:
Originally posted by Old Skool
Also, for 30% you may want to consider installing an extra head shim to help combat detonation.
An additon of 0.2mm Cu head shim for 30% Nitro usage is recommended.
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Old 04-28-2003, 09:58 AM   #7
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It's odd that your car would run leaner just by changing the pipe. As a matter of fact, the RDL Turbo pipe closely resembles the shape and size of the Nova (Rex, RB) pipe. I would check to make sure you don't have a leak at the exhaust port gasket. Make sure it's really snug. I've cut headers and changed out pipes on cars within the same race day and not had the dramatic temp change you're having. Also, 230 is a good temp area for this engine. If you're not flaming out, there really isn't a problem.
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Old 04-28-2003, 12:12 PM   #8
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I wanna know how good performance does the REX pipe has when it's used with the MR-12. Will there be a power gain if I change it with a Nova Mega TP 05. 10x
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Old 04-28-2003, 06:50 PM   #9
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I appreciate the response from everybody who contributed.

rod_b, I did find a broken exhaust port gasket, I'll try a new one and see if anything improves.

Oldschool & Eddiethefish, where did you guys get the head shim? The MR 12 Turbo never came with one.

Is it ok to use a #6 turbo plug with 30% or should I go with a #7?

Speed De, I think the REX is an excellent all around pipe for long and short tracks, I gives the engine a broad power band. I think what complimented the pipes performance was the modifications I made to the centax clutch. I used the following:

- Red clutch shoe from micro rc
- super hard MRX 3 clutch springs
- drilled holes into the clutch weights

One last ? to everbody, how does a broken exhaust port gasket degrades the performance of an engine?
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Old 04-28-2003, 08:17 PM   #10
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I was going to mention the clutch but someone beat me to it. I had a similar problem and narrowed down the problem to the clutch. Different pipes change the power band of the engine so you will have to change both your carb settings and clutch settings when switching out pipes.
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Old 04-28-2003, 11:01 PM   #11
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Quote:
Originally posted by PG
Oldschool & Eddiethefish, where did you guys get the head shim? The MR 12 Turbo never came with one.
There should be one...it's probably stuck on the bottom of the button and is so thin that it takes a close eye and the point of an X-Acto #11 blade to tell. I used another aluminum shim from an older side-exhaust .12 that I had sitting around (HPI .12R, as a matter of fact).
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Old 05-05-2003, 09:10 PM   #12
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I figured out the problem, it was the pipe!!! I took off the RD Logic pipe and put back the REX pipe, a #5 turbo plug, readjust the clutch and add an extra head shim (Thanks Old School), WALA, just had to richen the top end and lean out the bottom end, problem fixed. NOW, I'm not trying to say RD Logic makes a bad pipe, but I think the RD pipe will work better on modified motors and 5 port motors, I asume it will work on mine to if I cut the manifold to the MR-12 Turbo's preference plus rettuning the carb, but that's another big HEADACHE!!! Anyway, I'm happy with the REX pipe, it makes the engine easy to tune and gives a broad powerband. If anybody is interested with the RD logic pipe, I will sell it this weekend at Crystal Park for $25.00.
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Old 05-05-2003, 10:19 PM   #13
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Glad you got it to work well.
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