TimZ

Congrats on the numbers! One thing you want to keep track of when you start pulling fuel from the map while at the dyno is your manifold air temp (MAT) - did you happen to log it, and is your fuel injection compensating for MAT? The reason I mention this is that it's really common for the MAT to run significantly higher on the dyno than it does on the street, due to the difficulty of getting the same amount of air through your intercooler. If this is not being compensated for, you will end up running 1-2 points richer on the dyno. If you pull fuel from your map to correct this while on the dyno and then go back out on the street, you could end up 1-2 points too lean, which is not good:shock:

Well, since I've pretty much gotten my fresh rings broken in, and then the E85 tune nailed down, my 275/40-17 Victoracers are toast - noticed the cords starting to show today. The main problem is that I drive primarily on the street and want to have a tire that can be driven as such, so track-only slicks are off the table. I already realize that the horsepower and torque I'm seeing from the E85 (my guess at this point is around 500lb-ft and 650hp to the wheels) is going to overpower pretty much anything in this size. I'm also starting to admit to myself that even though I like going to the occasional autocross and want my car to handle well, the majority of "fun" that I have in the car involves straight-line acceleration. So here's what I've been thinking about and I haven't been able to find much on the subject... I currently have victoracers - 255/40 front and 275/40 rear, which is a combo that (all else equal) should tend towards understeer, but I needed the extra tread in the rear for longitudinal traction. I'd like to find a tire that gives up a bit of lateral traction to gain an advantage in longitudinal - but not so much that the car would be a disaster if I wanted to track it. I'm wondering if there is a drag radial out there that could give me better straight-line traction than the victoracers (they aren't bad to begin with, so maybe not), and still be reasonably competent at a track day or autocross. So the idea would be keep the victoracers in the front for the time being, since they aren't in bad shape and go to a drag radial in the rear and hope that I can maintain enough lateral grip from the extra width to compensate for the drag radial's longitudinal bias. Anybody have any ideas/experience with any of the latest drag radials? Do any of them maintain acceptable lateral capability? My fear is that it would be an all or nothing proposition, and I'd end up giving up too much lateral capability in the rear and not gain much (or any) longitudinal grip over the victoracers.

He did, in the context that it was a bad idea to block the bypass hole.

Not me - as you said, the push on hoses are much easier to work with and have more than adequate pressure capacity. Plus, it's lighter and doesn't eventually destroy everything it comes in contact with. I'm slowly in the process of converting all of my SS braided hoses to either push-lok or the Nomex-braided hoses(Start-lite, Pro-lite, etc) etc.

Interesting solution - just a couple of comments on the hose routing, though... Hopefully it's just an illusion from the pic, but it sure looks like the hose from #5 is really close to the exhaust manifold. Standard SS braided hoses are only good to ~350degF. The coolant flow through the inside should help some, but the SS braid will transmit heat from the exhaust manifold directly into the outer sheath. You should at least put some firesleeve over that section. Also, probably a non-issue, but it looks like you have a pretty high loop in the hose from #6, which might make it difficult to get trapped air out of it. The fact that it's routed back to the lowest pressure point in the system should mitigate this. Just remember that the water has several choices as to the return path it takes. If it ends up taking a bigger pressure differential to push the trapped air out of the hose than what is present, the water will simply find a different path and the air will stay in the hose.

Ahhhh... "Boost Compression" - the internet legend that refuses to die. There is a good discussion on this subject here: http://forums.hybridz.org/showthread.php?t=114598

That works. I was mostly curious - people often get confused about which way the fluid is flowing. No, it still matters - there is an amount of pressure due to the head of water in the system (density of the water vs the difference in height from one port to the other) that must be overcome, but the water will ALWAYS flow from a high pressure point to low pressure if it has a path to get there. It doesn't have a choice. That's why I specified "on the engine, aside from the pump inlet". The pump inlet is by definition the lowest pressure point in the system. These are just two different ways of saying exactly the same thing. You can't have liquid flow without a pressure difference, and you can't have a pressure difference in a body of liquid without flow.

I've seen them before but didn't have one on my non-California '78. I've often thought of finding a pump and bracket and re-plumbing to make it a vacuum pump for crankcase evacuation. If I had more package space in that area, it might be worth a try, but alas...

That's the lowest pressure point on the engine aside from the pump inlet - where does the turbo return the coolant to?

Not sure how long that would live, given the proximity to the exhaust manifold. The LS has crossflow heads, so the intake is isolated from the exhaust manifold heat. I guess if you are only talking about the plenum itself it might have a chance, but I'd think you'd want to do some serious heat shielding.

True, but the water still has to travel back to the front through the head from #6 to #1, so by this logic #6 should be the coolest cylinder in the head. Not sure what you are saying here - if the short circuit you are referring to here is a piece of hose bridging the two hose barbs in the engine that used to run to the heater core, then you would be running the hot water from the back of the block back to the pump inlet.

I've pointed this out several times before, but the CR only accounts for maybe a 3 hp difference when off boost, probably much less below 2300rpm. The simple fact is that either engine (NA or turbo) doesn't make much power below 2300rpm, and it's just more noticeable when the boost comes on. As other have mentioned, you need learn to stay above the boost threshold if you want to drive fast. The magazine articles of the day did their acceleration runs by brake-torquing against the auto trans and getting the turbo spooled before launch, and they usually mentioned this in the article. That, coupled with being able to stay WOT while the auto trans shifted gave much better acceleration times. For more normal driving, the manual probably feels more responsive even on the turbo, since you never have to wait for the trans to catch up.

I think it also goes by "JB Weld".

I agree. Honestly, I've never understood the obsession with trying to run slightly higher CRs for supposed off-boost gains at the expense of max boost. IMHO, the benefit of the higher CR is way overblown in these cases. If you do the math the power gain in going from 7.3 to 8.1 CR (which is what we are talking about here) is about 3.6%. On an engine that peaks at around 120rwhp without boost, we are talking about maybe 4 horsepower in the off-boost region. ...So you gave up say 60 hp worth of boost just to gain 4 hp when off boost. Yay.

Apparently I was mistaken on the polarity thing - however I'l still stand by the other comments - I would not recommend splicing the heater into the existing wiring, and especially not into the ECU ground. Introducing a significant amount of current into the ECU ground is very likely to cause a ground shift and potentially mess up many if not all of its sensor readings.

On a 4-wire EGO the heater is separate and doesn't have polarity. On a 3-wire EGO the heater shares the ground with the sensor output, so it does have polarity. Also, since the heater can take a fair amount of current it would probably be better to feed it its own power and ground rather than trying to use existing wires of unknown current capacity.

I would think it would work just fine. The only problem I can think of offhand is that it only has one general purpose output, so as long as you don't need more than that it should be fine.

If he doesn't have a direct ignition setup, then he'll still need something to hook the spark plug wires up to...

okay - that makes sense. I wouldn't consider using it without fixing the cracks.

I guess I'm a little confused - I don't think there is anything different about the valve seats in the P-series heads, so by that logic, you shouldn't run any Datsun head with a turbo. If they are filling and milling the cracks between the valves then you will most likely get new seats anyway, so just make sure they are installed with a really tight interference fit if you are worried about that.

If you must run a dizzy, then you should be able to make the n/a one work - lose the vacuum advance and lock down the mechanical advance. You should be controlling the timing exclusively with the Haltec. What does your advance table have in it?

yep

Hey Jeff... Something I've been meaning to ask - I'm curious about the effect of the air making a 90 degree turn before entering the IC. I would guess that there would be a density distribution such that there is more air towards the outside of the turn. So, for instance, your setup should split the airflow pretty much in half, but if I did the same mod to my IC above I think I would end up biasing the airflow to the bottom half. Would it be a big deal to re-run this model with a 90 degree turn before the splitter just to see if this works out like I think? Maybe one with the turn oriented like you setup and one like mine?