TimZ

Okay, I guess this horse just wasn't quite dead enough... One thing that is still bothering me about the comparison that was made between the N and P series heads was the statement: ...and at least a couple of other allsuions to this same point. Since this was said several times, I have to believe that this is what was meant - i.e., P-series cut .110" vs. N-series uncut, everything else the same. What I'm getting at is that it appears that no effort was made to check the actual valve event timing between the two setups. I did the math for this, and as it turns out, milling the head by 0.110" will retard the cam timing by about 5.6 crankshaft degrees. This is quite alot, and is definitely enough to render any difference in the head itself completely irrelevant. My personal opinion is the same as JohnC's - the only relevant comparison to be made here is stock vs. stock - once you start talking about modifying the heads, then all bets are off.

This is what I did, as well. However, I'm not at all convinced that it was necessary. If you look at the construction of the front cover and the shaft, the bearing surface that Doug mentioned keeps the shaft from climbing out, anyway. Also, there is no bearing up by the distributor mount point - there is enough clearance that it would be impossible for the shaft to bind there. Perhaps if the shaft wobbled very badly it could cause a problem at the lower bearing surface, but this seems unlikely to me. This was on a 280 front conver - perhaps older/newer engines had a different front cover design? I don't think so, though.

No, it's not true. I think whoever said that was joking. The question originally had to do with the fact that the manifold in question was severely hogged out, to the point that it was probably paper thin in places.

I hate to sound skeptical, but that does not look like a T-series to me. The compressor housings for the T-series are much bigger than that. I'm not able to see the last two pics, but I'm pretty sure that I see an internal wastegate actuator on the turbine housing in the fourth picture. Now, I know that I don't know everything, and there is probably more to be had, but I am having serious trouble believing that I have somehow left ~300hp on the table...

Donna brings up a very good point. After reading her post, I went and looked at the compressor maps. She's right - the 62-1's map doesn't even go to a 3.3 pressure ratio - the hightest point on the map is more like 2.9. Also, it's compressor map just barely touches 70lb/min (actually, it looks like it maxes out at 65lb/min to me), at it's lowest efficiency levels - just like Donna said. 62-1 Compressor Map The T66 does look like it has a much better chance of making 70lb/min at a reasonable efficiency, at a 3.3 PR. At least it's map goes there: T66 Compressor Map A couple of additional points about the maps: First, the cfm rating is referenced to flywheel horsepower, so we were not talking apples and oranges there. Second, the compressor maps tell you generically what the compressor will do. You then need to take into consideration the characteristics of the engine that you are attaching it to. The max flow rating for any compressor occurs at a specific, fairly narrow range of pressure ratios. At any give PR and intake temp, your engine will flow what it will flow - no magic here. If your engine will not flow that many cfm at that PR, then you simply never get to that place on the map, and the compressor flows less. In the case of the 62-1, for instance, it looks to me like the closest point to 70lb/min occurs at a PR of ~2.4. This is nowhere near the 3.3 that Jeff was looking for. At at PR of 2.4 (~21psi), Jeff's engine flows enough to make - ummm - I think it was ~415rwhp - remember? End of story. Please keep in mind that the efficiency ratings are not academic. Low efficiency = high heat, by definition. Planning for a high heat solution, when alternatives exist just doesn't seem very prudent, especially considering the compressor has not yet been purchased, and no cash has yet been comitted.

Add me to the list of people that don't like that idea ... The fact that the wastegate will maintain the boost at 8psi has no bearing whatsoever on whether it will maintain boost at higher levels. Remember that adding a turbo makes your system non-linear. The more boost you run, the more airflow you have. The more airflow you have, the more boost you run. And on and on, until something breaks. Without a wastegate, the system is actually unstable from a controls point of view (poles in the right half plane - that sort of thing). When you limit the boost pressure to 8psi, you are severely limiting the amount of flow through the engine, and a small wastegate will work just fine. You could probably get by with a 25mm gate at this level. As you start running the boost up, the airflow increases exponentially (if left unchecked). So, it becomes harder and harder to control the flow through the turbine, and more and more exhaust gas needs to be dumped away from the turbine. You really need to go by the horsepower level ratings (horsepower is referenced to flow, not boost pressure) that are given for the various external wastegates, and remember that they are talking flywheel hp for these ratings. Like I said before, I would not even consider anything less than ~45mm for a 600hp engine. It may seem like overkill now, but believe me - it's a huge pain in the ass to change this later...

I don't think it has any specific meaning, aside from being equivalent to "kick your ass". I think James just likes the way it sounds...

I think you are talking about the bearings here? If so, they are supposed to be there - that's the way they came from the factory. They weren't added in later.

Yeah, I was kind of tired when I read that - probably overreacted. Jeff - should I infer that this is somebody from Unorthodox Racing that is making you a dampner? If so, I just have to say that I'm a bit leary of them - is this piece actually going to be a dampner (with some sort of mass-spring system), or is it just going to be a pulley? I'm asking because I've never seen anything but pulleys from them. This is kind of important, since the stroker crank ought to be more prone to torsional vibration due to the longer crank throws. This is most likely the reason that strokers seem to be be more prone to breaking dampners. Going to a pulley with less damping (actually no damping) will just make the situation worse for the crank. If you just need a single groove pulley, the ATI piece looked like a better idea. Now if somebody just made a dual groove pulley dampner- I'd like to keep my AC if I could... Now, maybe I'm way off with my notions about unorthodox, but from what I've seen about them from different forums, they seem to be able to machine a very nice looking piece, but there doesn't seem to be much in the way of R&D to back them up.

Not sure what that's supposed to mean - I didn't know I was suddenly the enemy. Those are very impressive numbers, Jeff - congrats.

Well, there's no question that they can work some magic on you wallet - but I think there is a big question as to their price/performance. I have yet to see any dyno comparisons that unequivocally show more than ~1hp difference. Okay, maybe on some really badly cast stock manifold somewhere, but I have serious doubts as to whether this actually works measurably better than a decent manual porting/smoothing job that you could do by yourself for free.

Along these lines, I prefer to think of pressure as simply the byproduct of trying to flow a given amount of air through the restriction of your motor. The less restriction, the less pressure is needed. If you think about it, 600cfm through a 2.8 litre motor and 600cfm through a 5 litre motor will both result in pretty much the same output power from both - the manifold pressures required to get there will be quite different, however. If you try to run the same manifold pressures in these two motors, the output will be vastly different. I think people get hung up on the pressure thing, simply because pressure is what gets regulated in order to keep a turbo from running away. This point is more obvious on supercharged cars - generally, for a given supercharger, the boost pressure comes out to whatever is required to get the supercharger's output through the engine. As a result, less restrictive engine setups usually result in lower boost pressures, but they also usually yield more power. Okay - the compression ratio is what determines the combustion efficiency of your engine (i.e., how much power you get by burning a given amount of fuel). Higher compression ratios are more efficient. The problem is that higher compression ratios also result in a higher temperature rise as the fuel/air mix is compressed. If you go too high with the CR, the temperature of the fuel/air mix will get high enough for it to ignite, causing detonation. Interestingly, if you look into the thermodynamic equations for the Otto cycle, you'll find that the amount of temperature rise is dependant ONLY on the Compression Ratio, hence the final temperature at TDC is determined by the temperature of the air at the beginning of the cycle, and the CR of the engine. Contrary to popular belief, it is not dependant on the pressure that you start at. Read that a couple of times before shouting that I'm full of sh!t . The problem that turbocharging adds is not the pressure, but the fact that it tends to increase the starting temperature of the combustion cycle. Okay - well I thought it was interesting, anyway. As far as the combustion chamber size thing - do you mean displacement, rather than combustion chamber size? They are two different things. Larger displacement will do the stuff you mentioned re: getting more air/fuel in. However, a larger combustion chamber by itself will only result in a lower compression ratio. While this will give you more resistance to detonation for the reasons stated above, it does not cause more air/fuel to get pulled in.

Okay - I'll chime in... First off - I understand what you are saying, and I'm not offended in any way by what you said, but I do need to make a couple of comments... Yes, I'm using a modified exhaust manifold, but the turbo is mounted where the stock turbo was, albeit with a T4 flange. The wastegate is underneath. Take a look at Joel's manifold above - it's very similar to mine. The manifold has been ported to allow better flow near the turbine inlet, and the wastegate is positioned to give the least disruption of flow. I simply like the robustness of the cast manifold, and haven't been terribly interested in changing to a header (James gives me sh!t about this about every other time I talk to him ). As far as the power heading downhill after 6000, yes, it's all the way down to ~380rwhp by ~6200 - (pretty doggy, I know ). Please bear in mind that I am not using anything particularly special for a cam - it's just an Isky L475 grind - their mildest turbo cam, retarded 3 degrees. I use it because I like it's driveability - it gives good part throttle respose, pulls good vacuum, and still has decent (but not spectacular) top-end. Also, you keep talking about not making decent power until 4500. While my curve doesn't start to flatten out until around 4200rpm, I'm making over 300rwhp from 3800rpm up. Yes, it's a pretty rapid rate of change there, but the point is that you don't have to wait as long as you might think. Is my car driveable? I guess I don't know what your criteria are. For the most part, the off-boost response is quite good - the low compression doesn't hurt here nearly as much as people seem to think. Also, the car drives pretty much like a stocker when I'm at part throttle - which is exactly how I want it. Will it pull hard from 1000rpm in fifth gear like a Viper? Nope. Will it pull hard if I put it in the right gear? Yep. Is it hard to get the boost to come on? It's never seemed to be much of a problem for me. As far as turbo sizing - I guess I'm not that familiar with the T3 turbine housings that are currently available, but it seems to me that it's unrealistic to expect one of these to be able to get you to full boost at 3500rpm on an L28, and then have low enough restriction to flow 600hp's worth of exhaust gas at a reasonable turbine inlet pressure. A large wastegate will help here - I wouldn't even consider anything smaller than ~45mm. However, that big compressor is going to need alot of power from the turbine in order to make 600hp worth of airflow at a PR of 3.3. The end result will probably be that this will require fairly high turbine inlet pressure. The problem here is that high turbine inlet pressures (more specifically, a high exhaust/intake pressure ratio) are what makes turbo cams sensitive to valve overlap, which is what makes it hard to get a turbo cam to make power on the top end. The bottom line is that we don't have the luxury of variable valve timing or even switchable intake runners, and they don't make a variable A/R turbine that will support that kind of power (I keep hearing that they are really unreliable, anyway). So, if you really want to get to 600hp on your L28, you are going to have to make some compromises. Here's something that I've wanted to try for a while - it should be possible to take a split tangential turine housing and modify it so that one of the halves has a flapper door in it. You might be able to modify a T3 internal wasteate assembly to do this. Anyway, you could then control the exhaust flow through half of the turbine, and effectively alter the A/R. It would probably be a pretty much on/off kind of thing, but you could get your A/R to go from, say, 0.5 with the door closed, to 1.0 with the valve open. This should go a long way towards giving good low en response, while preserving top end power.

Wow - looks a little different from the last time I saw it... Nice work, Scotty.

I'm running a manual trans. I'm using a clutch that I got from Clutch Specialties. It's basically ACT's strongest pressure plate with a full face, sprung hub iron disk. So far, I'm very happy with it - engagement is very smooth, pedal pressure is firm but not objectionable, and it gave me no problems on my last dyno runs (or since). It is supposed to be good for 500lb-ft.

Okay, Shane, now I believe you . What I meant by 'streetable' was exactly what you just described. A turbine and A/R combo large enough to give a 1:1 pressure ratio will generally have a difficult time making boost at low rpm. Basic Physics. Most people seem to like to make their power at lower rpms for the street. Your combo should be able to make exellent power, though. My guess is that you should be much more tolerant to different cam grinds, and be able to tolerate more valve overlap. This should allow you to move your torque peak higher, which would give you even more power. I would guess if you made a sh!tload of power from 4800 to 7500rpm, nobody is going to be too concerned about lag (just pick the right gear, right?).

i was told by the company that does my turbos that the presure should NOT exceed 1:1. if there is 20psi at the intake backpressure should never be more than 20psi and the right turbo will have NO backpressure. when i maxed out my turbo 3 upgrades ago we put a gauge in the exaust manifold. at 15psi at the intake the exhaust had more than 30 psi back pressure. now at 25psi intake, i have 5psi at the exhaust manifold. unless the turbo is not sized right you should not have more pressure in the exhaust manifold. shane Where were you measuring the backpressure? You're telling me that you had 5psi at the turbine inlet (not at the downpipe) with 25 psi at the intake manifold? Sorry if I sound skeptical, but I'd check those numbers again... Your numbers make sense if you are measuring at the downpipe, but it's pretty difficult to achieve even 1:1 at the turbine inlet and maintain a streetable setup.

Do you have the Ford part number for your MAF? I might be able to help...

Just a minor point here - unless you are running a really large turbine and A/R, the pressure in the exhaust manifold will be higher than that in the intake manifold. Because of this, the intake charge will not blow out the other side. Instead, the exhaust will back up into the cylinder during the overlap (reversion). The end result is pretty much the same (long overlap = bad), but the cause, and therefore the available solutions, is different. This is a common misconception - probably mostly because this is what happens with a supercharger, since it does not have the high exhaust manifold pressures to deal with.

Scotty... For the amount of boost you have been running, you really should heed everybody's advice and go to at least the BPR-7ES NGK. I'm running -8ES's on mine. The -6ES plugs are too hot for your application - this can make you more detonation-prone.

I was just thinking the same thing, Tom...

Interesting - do you know what the issue is with the 6-12 month seal replacement? Is this due to all weather useage/high mileage, or do the seals just dry out? I ask because I have been using the AZ ZCar setup (Wilwood Superlite/Dynalite) since around 1988, and have only replaced the seals once, and this was simply to go to the newer o-ring design for decreased rollback. My car does not normally see inclement weather and is garaged in the winter. As such, my miles/year are pretty low. That said, I've never had a problem with this.

Zephram I was thinking Rube Goldberg... Isn't that a playstation on the lower right? Isn't it kind of stupid to have the NOS bottle sitting right next the driver's seat like that?

Like Scotty, I'm having trouble imagining that going to a 3" exhaust should be causing this much trouble. One thing that I haven't seen mentioned is the exhaust plumbing for the wastegate outlet. How big is the wastegate exhaust pipe, and where/how is it blended back into the main exhaust? Have you checked for blockages here - this would cause exactly the symptoms that you are describing.

I thought I remembered them claiming 390 rwhp - don't remember the torque... And I agree about those numbers - that would put the horsepower peak a fair amount above 5200rpm. I wouldn't think that would be terribly easy to do with that setup.