Noob Alert

[edin]

First post on Ratsun; I expect a warm welcome. Picked up a '71 510 Wagon last Friday and have put 1020 miles on it. Two main things it needs is a new oil pan gasket and a new exhaust. I'm dealing with cardboard and a continuous refill of the oil for now, but I just ordered my 31" Thrush glass pack and Magnaflow turbo muffler. Running 2 1/4" piping throughout. Cannot wait to replace the tiny tubing that's slip fit (well, slip fit is generous. it's most like loosely fit) piping.

 

Short term plans are to make sure it is mechanically sound over the next eight weeks at which point I need to get myself back to school in New Hampshire. Currently in San Jose, CA. Drove out here in a buddy's golf tdi and lost fifth gear around Salt Lake. Lost ignition switch (and all accessories) at Tahoe...I can't imagine what troubles I will find on a 3000 mile trek in a 42 year old car. Especially since today I took a right turn and heard "ping ping ping" and saw something shiny cross the other lanes. Have all my lug nuts, I couldn't find anything in the road...

 

Anyway, stoked to be a Datsun owner. Have been a long time admirer of JNC, had a '72 FJ40 that i just sold. As a college student who has recently turned from gawking at cars to wrenching on them, I know very little and have a lot to learn.

 

Yes yes I know, pictures pictures pictures. Lost my SD card and camera charger. Smartphone kicked the bucket. I'll get some up tomorrow. Classic first post amirite?

 

[flatcat19]

Your welcome would be warmer if you had provided pictures.

[Ratwagon1600]

Welcome on board Edin!

 

Get your act together and post pictures :)

 

Great to see your going to concentrate on mechanical stuff first.

 

Plenty of great info here (just try the search button first).

[KlassicMotion]

Welcome.

It's great to hear your driving your car.

 

My two cents:

 

If your engine is a stock L series, you may not want to go bigger than 2" exhaust pipe to keep the low end torque....  The 2.0L L20b engine ran 2" pipe from the factory.

[banzai510(hainz)]

2 inch and a stock turbo type muffler(Dybomax Super turbo) on my 521 also a resonator would be ezer on the ears.And will flow more than enough. I have twin Mukunis and only run 1.75in into a stainless UltraFlow Dynomax

for 18 year old its works good as i can hear you cooming before I jump out your girlfriends window before you come home as I hear you a mile down the street.

[datzenmike]

Large diameter lowers the exhaust gas speed and you'll loose some bottom and mid range torque not to mention sound like shit. Higher gas speed draws more left over exhaust out of the cylinder. Stay close to stock for the small L16... even 2" is a bit big and better for the larger L20B.

[edin]

Thanks for the input, everyone. I thought I had done my homework searching the exhaust forums. Maybe I"m mistaken or had selective seeing, but I thought there were a bunch of people who were running 2 1/4" to Magnaflows on their L18s. Parts were ordered on Summit yesterday at 5:30 and are on the truck for delivery already...

[datzenmike]

A stock pipe with 1/4" more is fine. This is because doubling the diameter will increase the pipe crossectional area by 4 times, not double. A small change makes a huge difference.

 

A 2" pipe has an area of 3.14 square inches

A 4" pipe has an area of 12.56 square inches.

 

I'm guessing the 510 exhaust is 1 3/4" this is 2.4 sq. in. Increasing to 2" is 3.14 sq.in. or an increase of just over 30%!!!!!!! See what I mean?

[KlassicMotion]

I commend you for searching the other posts first for the solution to your issue.  A lot of people post questions before doing any research...  Personally, I say after doing some research, don't hesitate to re-ask a question.  You may have a question similar to others, but your application may differ slightly and thus warrant a different answer. 

[edin]

Alright so y'all are right; the exhaust thread most people are running 2", some people are happily running 2 1/4". What happened was I mentioned that to a friend of mine who is helping me do the exhaust and he said to just go with 2 1/4 so I did. so I literally have everything in my hands: 3 lengths of 48" piping, u bends, thrush glass pack, and magnaflow xl. Do i return everything and pay in shipping?

 

Is it a backpressure issue? exhaust temp issue? Could/would a restrictor plate do something?

 

The thing is, I'm trying to take in all the advice I get here because, fuck I don't know. But I'm trying to avoid shipping costs back to Summit-- these pipes are heavy...I'm also trying to get it done this weekend since I have the time and this guy's shop to get it up in the air and such. Hopefully y'all understand the situation and that I'm not trying to trump your recommendations

[mrbigtanker]

This thread should now be in the exhaust section,post some pics or get out of here.lol

[KlassicMotion]

Alright so y'all are right; the exhaust thread most people are running 2", some people are happily running 2 1/4". What happened was I mentioned that to a friend of mine who is helping me do the exhaust and he said to just go with 2 1/4 so I did. so I literally have everything in my hands: 3 lengths of 48" piping, u bends, thrush glass pack, and magnaflow xl. Do i return everything and pay in shipping?

 

Is it a backpressure issue? exhaust temp issue? Could/would a restrictor plate do something?

 

The thing is, I'm trying to take in all the advice I get here because, fuck I don't know. But I'm trying to avoid shipping costs back to Summit-- these pipes are heavy...I'm also trying to get it done this weekend since I have the time and this guy's shop to get it up in the air and such. Hopefully y'all understand the situation and that I'm not trying to trump your recommendations

 

Maybe someone else can better answer your question, but from my experience, the biggest concern will be back pressure, and loosing the low end torque. 

 

..... I might suggest, that if your in a hurry, and you don't want to return everything, maybe you go ahead and use the mufflers, but put in 2" pipe.  You can get 2.25" to 2" reducers at the parts store (quick and easy), but for the pipe, if your in a hurry, you may have to go to the exhaust shop and get some.  Though the exhaust shop can can flare the 2" pipe to 2.25" if you know where you need the flare at. 

 

I had my whole exhaust with the muffler done at Midas for $200. 

 

Exhaust work is actually a science.  Most guys guess and do alright, but there is a lot of technical shit going on with the exhaust.  All engines vary a bit.  For instance on my V8's I run 2.5" From the header to the mufflers, then 2.25" back from the mufflers.  This allows the hot expanded gasses to flow from the header with the most volume.  But running 2.25" from the muffler gives the back pressure needed to keep back pressure on the cylinders. 

 

With my L20B, I'm running 2" straight off the header and it works well.... 

 

I don't have any experience with restrictor plates, but I don't believe it will do what you want it to, to get the most out of your exhaust. 

 

I know your doing a wagon, but this is what you get for $200 on a Sedan with L20B and 2" with a turbo muffler.  I had them bolt the muffler on so I could easily swap it out if I didn't like it.  We also left enough straight pipe before the Mustache bar so I could put in a resonator if needed.

[/u

RL]

[datzenmike]

If you have the pipe run with it. Not the end of the world.

 

Properly sized pipe will have a high gas speed and like something traveling at high speed it tends to keep going and can't stop very easily. The exhaust is traveling so fast that it tends to drag every last bit out of the cylinder making more room for the next charge of gas and air from the intake. There is less exhaust to dilute the gas and air coming in. A large pipe has slower moving gas speed and there is more exhaust just hanging around when the piston reaches TDC and the exhaust valve is closing. 

 

A larger pipe will benefit a very high revving engine as it is less restrictive so it is understood that a smaller pipe at some point is restrictive to flow at high RPMs. Car makers have to pick one size for good economy and all round performance to get good running at normal speeds. The ideal exhaust would be small diameter at low speeds and get larger as the engine revs up.

[edin]

Thanks for the help, everyone. Looks like I might not get to it for a couple of weeks so I may keep the 2 1/4" glass pack and muffler but exchange the pipes. We'll see. Anyway, got confirmation last night at 11pm that I need a new exhaust when I was driving in the left lane on the 101 near San Francisco and the exhaust dropped... Managed to drag it without any damage to the underside of the car (or really the exhaust). Ironically, I took out the exhaust in the parking lot of a smog shop and drove home. Can't wait to put in my new exhaust, now more than ever.

 

So here's the story. I had a Land Cruiser that I took down to the bare metal and repainted as a weekend project in high school. It taught me nothing about cars mechanically, and that was a huge mistake because I had spent all my money on cosmetic stuff and I had nothing left to play with on the mechanical side. This time, I'm going the opposite way. Maybe I went too far to the other end of the spectrum and I think, "What the hell; I'm in California and I picked up this rusty shitbox." There's not a single straight panel or rust free panel. BUT it is what it is and I'm excited that I won't be tempted to make this one look as nice as my FJ40 because it will take way more work than I can afford. And plus, I'm taking it back to New Hampshire where no car is going to go unscathed by the northeast weather.

 

At last, some pictures:

 

 

 

 

 

 

 

[DanielC]

Run with the exhaust pipe you got.    Although there is some validity to the "small pipe high exhaust gas speed theory", reality is this.   There are many other factors that affect exhaust flow.  And more backpressure is not a good thing.   If it was, you would see big block V-8 engines with 1/2 inch exhaust pipes.

[KlassicMotion]

Run with the exhaust pipe you got.    Although there is some validity to the "small pipe high exhaust gas speed theory", reality is this.   There are many other factors that affect exhaust flow.  And more backpressure is not a good thing.   If it was, you would see big block V-8 engines with 1/2 inch exhaust pipes.

 

Not more back pressure, just adequate back pressure.  There is a balance to be had.

[KlassicMotion]

So here's the story. I had a Land Cruiser that I took down to the bare metal and repainted as a weekend project in high school. It taught me nothing about cars mechanically, and that was a huge mistake because I had spent all my money on cosmetic stuff and I had nothing left to play with on the mechanical side. This time, I'm going the opposite way. Maybe I went too far to the other end of the spectrum and I think, "What the hell; I'm in California and I picked up this rusty shitbox." There's not a single straight panel or rust free panel. BUT it is what it is and I'm excited that I won't be tempted to make this one look as nice as my FJ40 because it will take way more work than I can afford. And plus, I'm taking it back to New Hampshire where no car is going to go unscathed by the northeast weather.

 

In my experience, as long as the car runs and drives, a nicely finished body and paint work is what sells a car.  Your average person can do the mechanicals, but most can't do paint and body well.  Many of the classic car sales lots I've been seeing lately, have inventory with nice paint jobs, but average, mechanicals and interior. 

 

I've got more examples, but I think my point is made....  In short, paint sells, but in reality, unless your working on something that's worth $$$$$$, your damned if you do, damned if you don't.

[Janksun]

The guy you bought thy car from is a good guy and put a lot of work into the goon. Good luck with it!