Need Advice: Engine Rebuild What Internal Mods needed for 400HP ??
12-14-2010, 05:43 PM
#31
Drifting
That was very good, thanks Chris. So one item you mentioned got my attention. Did most on my build already (motor in connecting lines and more lines now. Goal run and license next month. 25 yrs = no cat in Texas). However, got my attention on the oil cooler thing. I've cleaned and check my stock one but it's Texas, a street car and I am keeping my AC. Might care to suggest a replacement oil cooler?
The RX7 oil cooler also fits very well. Here is a picture of my coolers and their mounting locations. One is fan driven with a thermostat and the other is static. Chris white has a neat unit that is incorporated into a radiator. I believe this unit works in line with the stock unit.
12-14-2010, 05:44 PM
#32
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That was very good, thanks Chris. So one item you mentioned got my attention. Did most on my build already (motor in connecting lines and more lines now. Goal run and license next month. 25 yrs = no cat in Texas). However, got my attention on the oil cooler thing. I've cleaned and check my stock one but it's Texas, a street car and I am keeping my AC. Might care to suggest a replacement oil cooler?
12-14-2010, 05:58 PM
#33
Drifting
Not many choices – you can go with the KISS set up that is sold as a kit, make your own cooler, lines and mounting or go with an aluminum radiator with the oil cooler built in (I am a little biased to the last one! - https://rennlist.com/forums/944-turb...eferrerid=1956 )
12-14-2010, 08:16 PM
#34
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George D:WOW Do you have enough Mods for that car yet? Man can we call that a Porsche any more or have you created your own brand? I guess one thing leads to another in the world of 944 mods. I will use your car as a goal to attain some day. Looks pretty and I am sure very fast! Thanks for your feedback I will take it all into consideration.
Chris: Thanks for the honest opinion about the internal engine mods. I hope no ones panties got twisted as they read that. You don't beleive in the Oil baffle kit or cross drilling, very interesting. I was pondering that and then I examined your profile photo. I just don't think you corner hard enough in that 944 so hence no need for the baffle? AM I right?
Seriously what is your theory on this baffle kit and cross drilling? I find this very interesting as many others want to talk me into this....
Chris: Thanks for the honest opinion about the internal engine mods. I hope no ones panties got twisted as they read that. You don't beleive in the Oil baffle kit or cross drilling, very interesting. I was pondering that and then I examined your profile photo. I just don't think you corner hard enough in that 944 so hence no need for the baffle? AM I right?
Seriously what is your theory on this baffle kit and cross drilling? I find this very interesting as many others want to talk me into this....
12-14-2010, 08:34 PM
#35
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12-14-2010, 09:29 PM
#36
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Well, actually have done some oil cooler fab before but like 30 years or so ago in my cafe racer days. Before sport bikes we built our own. Had a Triumph 650 (dry sump with oil tank under seat) and made a custom seat with tail faring. Put an air scoop on one side, exit vents around the recessed tail light and mounted a VW type 4 oil cooler in it cross ways. Machined an aluminum plate that stood in for the engine part of the mount with rubber seals. Worked. Pal that got me back into the P car thing has a 914-6 and uses a Mazda oil cooler up front. OK. Fab and plan time. Oh, Chris, love your set up, very nice. However my radiator was no go so bought one last month from Rennlister and had bad tank. Combined and had flushed and sealed so have one very nice radiator now. One day I will have a driver.....
12-15-2010, 03:26 AM
#37
Special Tool tried this (cement) on one of his blocks. ST was a guy that showed dyno's in the 600hp range. Granted, at one event he hit around 400whp, and he lost to a 300whp 951 at a 1/4 mile event. If you search, you may see the race. A better option, if you are looking for a stronger designed open deck block is to add a deck plate. I think Garrity has one of his old ones at his shop for his race 951 motors.
I think ST went through two or three bottom ends trying to overcome the fact that his head couldn't handle the flow of air at those boost levels. It's not the ability of us to make a bottom end strong enough to handle 1000hp, it's the ability of our head design to flow the air. EVO bottom ends aren't as strong as ours as stock. Look at our cranks, forged rods, forged pistons as compared to the modern stock EVO or STI. It's their heads that flow enough air to allow nutty dyno runs. This DOES NOT mean a 600WHP EVO is faster at the track than a well sorted 350whp 951. I've owned a 400+ WHP EVO. My old blue 89 951 with 330whp was faster once moving.
Sent out a post to see if anyone in your area will let you drive a well set-up Porsche 951. I think you will have some fun in a 300 to 350 WHP 951 with modern suspension mods. Offer them free pizza and beer. You might have have a few folks show.
I think ST went through two or three bottom ends trying to overcome the fact that his head couldn't handle the flow of air at those boost levels. It's not the ability of us to make a bottom end strong enough to handle 1000hp, it's the ability of our head design to flow the air. EVO bottom ends aren't as strong as ours as stock. Look at our cranks, forged rods, forged pistons as compared to the modern stock EVO or STI. It's their heads that flow enough air to allow nutty dyno runs. This DOES NOT mean a 600WHP EVO is faster at the track than a well sorted 350whp 951. I've owned a 400+ WHP EVO. My old blue 89 951 with 330whp was faster once moving.
Sent out a post to see if anyone in your area will let you drive a well set-up Porsche 951. I think you will have some fun in a 300 to 350 WHP 951 with modern suspension mods. Offer them free pizza and beer. You might have have a few folks show.
About the flow of the 951's head. Why is it exactly is it that the head cannot flow the amount needed to easily make big power and compare to say an Evo like you said? I tried looking up pictures on google of Evo heads so I could compare to the 951's and the one thing that seems obvious to me is the fact that ours (951) are 8 valve heads and the extra intake and exhaust valve in the Evo would allow for a lot more air flow. Is that the main factor? The number of valves? Or is there more to the design of the entire head?
Im just curious if there is a more in-depth reason other than the what seems obvious answer, the number of valves. I would like to sound smart and impress the next time I am bench racing and the topic of 951's comes up.
12-15-2010, 03:47 AM
#38
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Stock heads comparison data:
951:
Intake ~180cfm
Exhaust ~ 190cfm
Evo 8:
Intake ~ 280cfm
Exhaust ~ 260cfm
Number of valves, CC & port design make the Evo head flow quite a bit better than our 8-valver.
951:
Intake ~180cfm
Exhaust ~ 190cfm
Evo 8:
Intake ~ 280cfm
Exhaust ~ 260cfm
Number of valves, CC & port design make the Evo head flow quite a bit better than our 8-valver.
12-15-2010, 05:12 AM
#39
Well thanks Rogue_Ant that's what I was looking for, some numbers to compare. Although I still want to know why exactly or what exactly is different about the CC & port designs...... I'm that annoying 5 year old that keeps asking "but why?" however that is information I should find with my own research, don't want to clutter the OP's thread with questions that don't benefit him. Peace
12-15-2010, 07:38 AM
#40
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I just got back from a hunting trip with some friends. I drove a friends 951 on the way home (200 miles) with about 330whp running Vitesse software, a very quick spooling Tial mounted Garrett turbo, good suspension, brakes, and it was really fun. The car had about 240K on this motor with nothing but a ring and bearing job. He is also running a 2.5 N/A head. Amazing. Immediate boost is so much better than lag with these cars.
12-15-2010, 08:20 AM
#41
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SirLaps, voodoo magic, millions of dollars, and some folks have spent a lifetime of pursuing the best CC/Valve/Porting/Intake relationship. You can research until you find the end of the internet. Let us know what you find in your search for why "exactly" they flow more/better.
I have a friend that owns a bunch of national championships in the motorcycle world, and he's not conducting tours of his cyl head room, and for good reason....voodoo!
I have a friend that owns a bunch of national championships in the motorcycle world, and he's not conducting tours of his cyl head room, and for good reason....voodoo!
12-15-2010, 09:54 AM
#42
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Chris: Thanks for the honest opinion about the internal engine mods. I hope no ones panties got twisted as they read that. You don't beleive in the Oil baffle kit or cross drilling, very interesting. I was pondering that and then I examined your profile photo. I just don't think you corner hard enough in that 944 so hence no need for the baffle? AM I right?
See picture below – both inside tires are barely touching the track – datalogging sees over 1.2g peaks. That car had 400/600 springs on coil overs with large swaybars & 370 rwhp all day long…..and if you had the high res version you could see the ‘I’m going to die’ expression on the student!
And that was on the street car. The track car(s) see more than that.
• Oil too hot (<- problem for anybody running their car hard)
• Oil foamed by hitting the crank (<- big problem for road racers)
• Oil pump cavitation
• 90 degree corners in crank oil passages
Sump baffling does not help any other those. Sump baffling mods were first used back in the 60’s when oil starvation became a problem for production based road racers. Some folks guessed that since the #2 rod bearing looked like it was getting starved for oil the oil pick up must be sucking in air. It wont’ happen on a 944 unless you are way low on oil – or you are hitting the curbs hard enough to put wheels in the air!
Cross drilling the crank – this is another common road racers answer to oiling problems – it also does not deal with the four main points. Your bearings depend on one hydrodynamic wedge to save their lives, if the oil pressure drops to the rod due to the 4 points listed above more holes in the crank will not help.
The best solution at this point is a dry sump system with an air oil seperator. Not cheap and not a good street answer. Everything else is band aids. Some band aids will help a little (oil cooling and windage trays) and many won’t.
12-15-2010, 10:04 AM
#43
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The 8v head actually flows very nicely at low to mid valve openings - it’s a great deign for midrange torque – which is exactly where our engines shine. Compare midrange torque output with any other engine at the same boost levels – you will see where Porsche’s engineering time was spent.
Once you see that you will understand why it is folly to try and make an 8v 951 head into a high rpm HP monster – that’s not what it was designed for. If you want a high rpm HP monster look to the 16v head!
12-15-2010, 11:45 AM
#44
How big is the influence from using higher octane fuel?
If assuming correct mapping how much more hp would be safe per octane unit?
I'm guessing that "pump gas" is 93 PON fuel which would equal 97 RON here i Europe. I always run 98 RON plus booster on the track giving 100-101 RON which would be 96-97 PON.
/Dea
If assuming correct mapping how much more hp would be safe per octane unit?
I'm guessing that "pump gas" is 93 PON fuel which would equal 97 RON here i Europe. I always run 98 RON plus booster on the track giving 100-101 RON which would be 96-97 PON.
/Dea
12-15-2010, 11:50 AM
#45
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