L28 vs 3.0L

[RacerX]

I had an opportunity to drive a couple of Zcars for sale recently that both claimed had Rebello engines. The first one I drove had a L28 with "bored out" SU carbs with a mild cam and some headwork. I wasn't that impressed. The other Z had a 3.0 liter - with the same modified SU's and headwork - both cars almost seemed identical in their engine mod department - and both didn't have to many miles on their engines (20-25K) I didn't notice any difference in performance between the two. I thought I'd feel more torque with the 3.0 but didn't.

 

Is there suppose to be that much difference in power between the two? I presumed there would be because of the increase in engine size. Anyone have any observations about this?

 

thanks,

 

RacerX

[jeffp]

well how well the N/A engine runs is dependant on the cam and how well the carbs are tuned. There are just so many different variables that it is impossible to say this is better then that. One thing to keep in mind thos is this, the 3.0 is capable of more power and torque then the 2.8, it's a matter of swept volume, and when you do the calculations, you will find the 3.0 will do more.

When it comes to a turbo application, I can tell you that my 3.0 is making the same power on 4-5psi of boost less then the 2.8 and it is way more torquer then the 2.8 for the hp readings.

[Dan Juday]

All other things being equal, or seemingly so as you stated, I would think it would take a dyno or a time slip to tell the difference between .2 litres. Gearing, tire compound, a little indigestion, can all have an influence on a seat-of-the-pants evaluation.

[TimZ]

When it comes to a turbo application, I can tell you that my 3.0 is making the same power on 4-5psi of boost less then the 2.8 and it is way more torquer then the 2.8 for the hp readings.

 

Is everything else the same between the two, as in identical? A 7% increase in displacement should only require about 1psi of additional boost in the 2.8. Maybe 2psi, but 4-5 sounds excessive.

[Dave240Z]

Unless the engine was also installed in an identically prepared car, your results will vary as well. For instance, did both cars have the same transmission, rear diff and tire sizes? These can affect how one engine might compare against another.

 

That said, a 0.2L bump in displacement is not much and I wouldn't doubt if it was hard to tell any difference with a "butt dyno". But due to the added displacement, the 3.0L does have more potential to make power. Whether or not that extra potential is realized is an entirely different story.

 

I can honestly say that the 3.0L Rebello in my car makes gobs more power than my previous 2.8L. But, in all honesty, it's not exactly an apples to apples comparison as there are more differences between the two engines besides a 0.2L displacement increase.

[Lockjaw]

Every time I have gone up in engine size starting at 2.4 liters, there has been a noticable difference. Something was probably off with the 3 liter or else the 2.8 was abnormally stout.

[jeffp]

All I can tell you is the JWT tuned both of these cars. My car was running 4-5psi less boost and making the same power the L28 was at a higher boost level.

Maybe that is why they called Robello an commented on the power my engine was making, and asked him about what went into the engine. I thought that was interesting at the time myself, and I only found out about it in passing talking to Dave about some other issue I was dealing with at the time.

I know what I did to my engine, and why it makes better power, and Dave also knows some of the things I did to my engine, but not everything. I went to great lenghts on the smallest things when I built the engine and it paid off for me significantly. The exhaust back pressure for example. Everyone I talked to and told them my results of my testing said it was exceptional, and uncommonly good, very good.

But again we get back to the basics, and swept volume is just that, swept volume, the more you have, the more potiential you have to make more power in any application.

I will say one thing tho, this last build I am doing on the car is going to be sweet, if I can manage to get the fuel management to support the hp potiential of all the new hardware. We will see, and I have been working on this stuff for to long and I'm getting sick of waiting.

[TimZ]

But again we get back to the basics' date=' and swept volume is just that, swept volume, the more you have, the more potiential you have to make more power in any application.

[/quote']

 

Yes, I agree. My point was it is unlikely that the swept volume accounted for all of the 4-5psi difference.

 

If, for instance, you were originally running 18psi and were now running 13 for the same airflow, that would imply an approximate 18% increase in airflow for a given manifold pressure. This is considerably more than the 7% increase in swept volume alone can account for.

[Guest zline]

okay...strokers are a big misconception even though there is so much info out about them. You will experience a power increase, although a small one. The increased swept volume and improved r/s ratio will provide for a more linear power/torque band. .300 (3.1) and .200 (3.0) will NOT be super noticable on a n/a engine with a mild cam and bored out SUs...to fully capture a strokers ability n/a you'd need a big cam (which requires new lash pads and valve springs) and either triple 48mm DCOE/PHH or FI

 

 

The fuel delivery is also based on your application. For a turbo stroker...FI, for big power n/a that you need to control its power band (through choke manipulation) carbs are the way to go.

 

Oh yeah, a turbo stroker is where you'll really really notice a difference in the linear delivery of power and more low end grunt due to increased displacement and s. volume.