L-28 dynojet

[inline6]

Graph of my L-28 dyno runs... power is at the wheels. I've seen some posts about 'how much horsepower should I have?' Perhaps my runs are a useful reference point given that my basic engine set up is a fairly common combination.

Engine is:

Stock L-28 (F54) with flat top pistons. (NA 280ZX short block)

E-88 head with very little removed from head gasket surface - just to true... Intake port matched to stock intake manifold, very minor porting on exhaust ports.

Manley stainless valves 1mm bigger intake (1.73'' I believe). Stock exhaust size. Stock valve guides.

Stock cam, stock SU's (with SM needles), stock air cleaner, stock air filter

Crane HI6 ignition

Clifford Research 6-3-2 header with true dual 2" exhaust and 4 magnaflow mufflers. Two 4" round in the driveshaft tunnel and two small ovals in the back.

Difference in the two runs is simply removing the air cleaner cover and filter.

Edited September 8, 2009 by inline6

[ozconnection]

Nice run! I've pulled many runs on my L28 and your runs are impressive for what is essentially a stockish configuration.

Do you attribute your peformance to any one thing/aspect in particular?

My interest is in your exhaust configuration which is the biggest deviation from stock from what I can see. Did you happen to have before and after runs after changing the exhaust system?

Your power increase after removing the air cleaners may indicate that your mixtures with them on are too rich, removing them allowing in more air and thus leaning the mixtures to a better/more powerful AFR. I would work on this aspect a little to ensure you get cold air consistantly and use the best and lowest restriction air filters available to keep that power peak!

Cheers!

[inline6]

I don't have before and after runs with this exhaust. I used to run the same header and two separate pipes that were 1 and 3/4" in diameter along with 4 glass packs. In fact, that system was the complete Clifford Research exhaust which was the old Datsun Competition Department's exhaust set up for the street. There is a picture of it in the "How to Hotrod and Race Your Datsun" which I scanned and include here

Years ago, I fabbed a straight pipe section which I put in place of the glasspacks while I was at the track. For the first session, I left the glasspacks on. During the remaining sessions, I switched to the straight pipes. In addition to a lot more noise, I noted the engine speed I could achieve on the back straight was several hundred RPM higher with the straight pipes. To me, that meant the street exhaust could be improved upon. That is why I went with two, 2" pipes when the old glasspacks wore out. It doesn't sound as nice, but the bigger pipes breathe better. The car revs out quicker in third and fourth and hits higher RPMs in fourth just like when I had the straight pipes on.

So, if my HP is a bit high, I guess it could be the exhaust. I think it could be mild porting in the exhaust ports too. I'm told a little work there makes a big difference. But then again, that port work was there before all the stuff about exhausts I mentioned above.