Compression ratio of Nissan ET...

[Myydral]

Greetings all. A friend has just bought himself ( details supplied by him ) a Nissan Pulsar ET 1.5L ( bored to 1.6L ), N12 about 1984 ish....

Apparently it goes alright but he needs to know the compression as the boost is running at 7psi at present but "it doesn't feel like it."

He wants to make sure verything is working as it should be...

This is as much info as I have...

Any ideas...cheers..

[NefariousLS1]

lol its a 1.6l whats it ment to feel like lol

[iamhappy46]

7psi into the ET E15 motor is not much. Also, if it is running the stock ECU and MAF, then things will not improve much even running 12psi except a lot of torque steer but it will never feel genuinely fast. There was one on the Pulsar forum running 15psi with a tuned Microtech on a T25 turbo and it was pulling mid 15 ¼ miles :rofl:

[matts]

From memory the stockers had somewhere between 7.5 and 8:1. Any indications on what other changes have been made internally? Shaved head?

[Wonky]

I know it doesn't answer your question but we had one of them for about 4 years in 1984. Was a very nice little car for its time. I used to think it was fairly quick for what it was but compared to now it was a slug! :D

[Alister]

Pretty sure N12 ET was 8.0:1, higher compression ratio would go better though...
Can't expect too much out of em, 70oddkw, 150oddnm, not a lot even though its pretty light.

[RB30X]

7psi into the ET E15 motor is not much. Also, if it is running the stock ECU and MAF, then things will not improve much even running 12psi except a lot of torque steer but it will never feel genuinely fast. There was one on the Pulsar forum running 15psi with a tuned Microtech on a T25 turbo and it was pulling mid 15 ¼ miles :rofl:

A pulsar forum:confused:, what a great place to find an answer to such a question.

[planetdavo]

It wont feel like a modern 7psi turbo engine, as the electronics of a modern turbo engine allow much higher compression ratio's.
Old school turbo's had to run such low compression that they have zero balls off boost, then it came in a rush of torque steer, and that was about it!
Still only a small engine with low compression remember, so it wont feel special compared to nearly anything newer.

[Tony Kendal]

I think they were about 9.2ish :1. about 175 psi on the comp gauge from memory when cold. The ford turbo lasers were about 8.5:1
I had one with a watson racing cam, intercooler, fully balanced and a different A/R turbo and 3 inch pipe -front to back- the drone was deafening. Did about 175 front wheel hp at 17psi but would go to 20psi. Torque steer like a bitch and went verrry well for it's time.

[GODSMACK]

I think they were about 9.2ish :1. about 175 psi on the comp gauge from memory when cold. The ford turbo lasers were about 8.5:1
I had one with a watson racing cam, intercooler, fully balanced and a different A/R turbo and 3 inch pipe -front to back- the drone was deafening. Did about 175 front wheel hp at 17psi but would go to 20psi. Torque steer like a bitch and went verrry well for it's time. 175psi - holy mother of god!!!

[VX2VESS]

not many of those around these days

[wrexed03]

Cant answer your question but i had one too. Must agree it was a fun car at the time. Went through 3 turbos on mine. It copped a caining. If he wants more go he needs to get the compressor wheel changed and the housing setup for it. I think mine was setup with a t25 wheel. Used to enjoy the torque steer.

regards

[planetdavo]

I think they were about 9.2ish :1. about 175 psi on the comp gauge from memory when cold. The ford turbo lasers were about 8.5:1
From Autospeed...
" Heart of the new car was the transversely-mounted, four cylinder, turbocharged E15ET engine. The re-engineering of the engine for its forced aspiration role was quite extensive. While it shared its long-stroke (76mm bore and 82mm stroke) swept dimensions with the naturally aspirated 1.5, there were many other differences. The strengthened con-rods were shortened by 3mm to reduce compression from 9.0:1 to a more turbo-friendly 7.4:1, piston rigidity was increased, the top piston rings were chromium plated (for improved wear resistance), and the gudgeon pins were strengthened.
A heat exchanger (through which coolant was circulated) was fitted to reduce oil temperatures, and an auxiliary electric radiator fan was used to blow cooling air over the turbo and exhaust manifold. The crankshaft had rolled fillets and the valve seats were stellited. The Nissan/Garret T02 turbo featured an internal wastegate and was one of the first of a new breed of tiny turbos designed for low-lag application on small four cylinder engines. It used a peak boost pressure of 7 psi, and as with other Nissan turbo engines of the time, no intercooler was fitted.
THEN, FOR UNLEADED...
From January 1, 1986, all cars sold in Australia had to run on unleaded fuel, with both the EXA and ET modified by the manufacturer to run on the lower octane brew. Although the compression ratio was raised from 7.4 to 8.0:1, peak power on the lower octane fuel dropped from 77kW to 75kW, with torque down marginally from 157 to 152Nm. (Both maxima were still developed at the same rpm.) For unleaded fuel, a catalytic converter was added to the exhaust and the engine management system gained an exhaust gas oxygen sensor. The turbo was significantly upgraded, with the previous air-cooled design being replaced by a water-cooled version."
Electronics of that era could not deal with hi comp Turbo engines like the current ones...
Now, is it time to go back to being a HOLDEN forum yet??????????

[iamhappy46]

The compression gauge would have showed more dynamic compression(175psi) due to the camshaft design with nearly no overlap

My SSS Pulsar with a variable valve timing and lift head, has 175psi on the compression gauge when the high lift/duration lobes are 'on' despite having nearly 13:1 compression as overlap is errr, rather excessive. The low rpm lobes, give 240psi :D

I know a popular swap at the moment is fitting the GTiR 172Kw SR20DET motor with a T28 into the little ET Pulsars and watching the front tyres melt like cheese in a microwave :rofl:

[Myydral]

Thank you to those who posted helpful comments...I shall pass this info along...