Compression test

[greenwood]

Rb20det. I've been running the engine for the past 2 years. Runs great, doesn't miss a beat. Recently did a compression test with the car warm. Came back as 130-140. Mostly 130. I'm thinking to myself, well just great. I wanted to slap a bigger turbo on but now the engine sounds tired.

My friend and I compression tested his sr with the same tool and he pulled 150 across the board.

My question is, is my engine still ok to go for 300whp? Seems to run just fine. I hear as long as the numbers are consistent it is most likely fine. I was thinking of looking into a rb20 spare in the meantime just in case this one pops, or swap a rb25. Basically advice on compression tests indicating the health of the engine would be great. Car uses no coolant or oil. Runs top.

[steve shadows]

150 really is not bad? Who said it was bad?

If it's 150 all the way across you should be ok.

Now the RB20DET pulling out 300 whp you'll need some good tuning on that thing with a properly sized turbo. I suggest a used PFC if you can source one for that motor and a 50 Trim T3/T4 on the cheap should do the job with some omre fuel pressure and slightly bigger injectors.

[greenwood]

I wish it was 150. Came back as 130-135 with the highest being 140. My friends car got 150 on the same guage 4 nights prior to this test

[steve shadows]

Don't take this the wrong way but did you make sure the throttle plate was open so that you could make sure enough air was being allowed in to fill up the cylinders under cranking? I have even made this mistake all-be-it a long time ago but this will throw off half of the results from the cylinders because the throttle plate will just block the air from coming in :picardfp:

[greenwood]

I hear you and yes I did

[greenwood]

Did a test with the engine cold
This morning just to see. 140 on all of them. I thought it was supposed to go down when cold

[greenwood]

I'm going to rack this up as poor battery/cranking amps due to my janky wiring. Car is at the same psi throughout cylinders and feels strong time for bigger turbo :$:trogdor:

[Darren]

if it's running fine, and not burning / smoking... you should be fine, but as was mentioned, tune is always the key. Don't just throw on a bigger turbo, jump up 1/2 bar and expect things to hold together without a retune :D

[greenwood]

Hahahah yes I am getting a base tune from Carl
H then a custom
Dyno tune, rb26 injectors etc.

Thanks!

[Kingtal0n]

here is my opinion.

RB20 engine is very rare to see, and even more rare to see in a running car.
The complexity of the swap compared to the displacement automatically turns the engine unfavorable- why not just install a 4-cylinder of similar displacement?

Some people just want to listen to it run, they would rather have an inline 6-cylinder in the car anyways. Ok, so you own one of the rare swaps.

Because it is so rare, I would not modify it. Not a nice OEM engine in a daily driver that is rare, possibly hard to find parts for. It ALL depends on the availability of parts.

If you have components to repair/replace then you are free to change something. Melt a piston? No problem I got 60 OEM pistons on the shelf, waiting & several long blocks available just in case I need anything else.

Otherwise- when you break a part, you are searching for it, and your daily driver is not driving. Have an extra car to drive instead? Then it wont matter as much to you, that is a convenience and weighs in the favor of modifications taking place, such as larger turbochargers and aftermarket computers....

[Kingtal0n]

Sir Bob:
Hi, my name is Bob and I own an RB20DET engine. I just bought the car with it. It has the factory turbocharger and computer and it runs great! I want to upgrade the turbocharger and make it faster. I don't have very many tools and I dont own a shop or a lift and I don't want to spend alot of money.

Kingtal0n:
Bob, please do not modify that engine, especially with a larger turbocharger! You cannot afford to replace that engine if a piston melts, which is quite possible considering the track record for RB engines whose factory cast components will NOT tolerate abuse! If it runs great now, just drive it and enjoy the sound of it, take care of it and change the oil every 2,200 miles if possible, maintain a functional PCV system and a proper high quality air filter, use a full face street clutch and maintain the A/C...

Many people are changing turbochargers instead of A/C components. I say go for the A/C and make it really comfortable to drive and enjoy the factory components, including turbocharger and ECU, install a wideband to keep an eye on a very important number when it comes to engine health, add some comfy seats, seal up the windows really good and replace the rubbers on the car to get it quiet inside.

If the engine is tired, high mileage, compression is low, oil turns black quickly, it has multiple leaks, it may be time for a real rebuild. If a quality low mileage longblock cannot be sourced, you will have to rebuild yours, and it will probably require machine work to bring certain tolerances back to OEM acceptable, or even just to acceptably clean the block, everything could be stripped down to the core and cleaned/replaced as needed. Everything must be kept incredible clean, and you should have the engine built in a room with air filters, like a room for painting a car, if possible. The cleaner the components are, and more precise the measurements are, the better the build can be. It is possible to turn out an engine that will go for 200,000+ Miles with very little maintenance, He used a dial bore gauge and checked the FSM for acceptable numbers before installing the crankshaft. Colors are noted, but compared, and wear was accounted for.

[fliprayzin240sx]

^^^WHAT?!?! Its a damn RB20, you can get a full RB20 engine set for less than an S13 SR go for. 140 psi aint exactly the end of the world on a low compression engine. I wont really freak out until that shit gets down to 120 psi or less.

Shit, if I have an RB20 and that shit blows, sounds like the perfect excuse to upgrade to an RB25.

If you're so worried you'll melt a piston, get that shit tuned properly. Its not uncommon to see RB20s make 400 hp back in Japan. Then again, most people get rid of them because there are better options out there.

[greenwood]

KingTalon sounds like my dad. Are you 62 dude? Lol

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I know all about the 20 and can work on them with my eyes closed. The 25 is a noce option, the 20 gets baller mpgs on the highway when road tripping. My rides are always tuned. I will be picking up another longblock in the next few months to sit on, maybe a 25 for when this engine eventually goes south.

I am going to modify it and already have. I am going to track it and already have. I am going to daily drive it and already do.

Thank you for the advice, but I know what I'm doing with my ride. I was just worried about the compression which i figured out to be poor cranking amps, probably from my janky wiring That I did years ago before I knew what I know now :). Anyways. RB's ftw. 20's too. A great dd. and so many ppl disrespect them. Who said I was trying to set land speed records. Just here to
Have fun and get my wrench on :)