3.4 Dyno Chart

[Jeff Alton]

Originally Posted by Carbster09

Any reason to go with 98mm pistons over 100mm? I am having an engine built and thinking 3.5? Also struggling with ITB selection, as there are a number of choices. I want something easy to maintain over all else.

I have a 915 box (engine will be in a 71T) ... stock gear ratios seem fine; any sense in re-gearing it closer / shorter? With this torque it would seem not.

The biggest reason is cost, trying to stay within a customer's budget. 3.2 95mm cylinders can be bored to 98mm and plated. This is a reliable and durable solution. Pistons cost the same either way. The 100mm we have used on a couple of 3.5 with good results also.

For ITBs, we have built a few motors with the Jenveys and really like them. We have also used PMO's but found they did not make quite the same power on similar builds. The PMO are very easy to set up mind you. The Jenvey's are also easy, but take a bit more time.

I am also quite intrigued with the Rasant Products ITBs. They look very similar to the Kingsler being used on the Singer and feature Idle air control which is nice. They also are available with an adapted 964 or GT3 plenum. Would love to do some testing with the plenum to get a first hand look at what happens to the power curve (have seen conflicting data).

Cheers

[Peter M]

Jeff,
The Rasant's ones look different to the Kinsler ones:

https://kinsler.com/Shop/product/porsche-itb/

https://rasantproducts.com/rasant-products-intake-system-is-6-individual-throttle-bodies/

They both look good though and I hope you can do a itb comparison with and without a plenum soon.

[slow car]

Calling motor builders,.While on the 3.4 subject.... i am ready to upgrade my twin plug 3.4, Je 10.5, GE 60 cam 46 pmo motor to 12.5:1.
My quandary is should i be going to a GE80 or more agressive still cams and 50 PMOs?

Full Areo slant nose Track,hill climb ,sprint use car, 2100lb, that i currently rev to 6500 RPM.
Any one have dyno sheets on these options. Experance to share?
Thanks

[faapgar]

I like the front treatment and the rear undertray.How about a shot of the rear straight on.More compression to 12.5 never hurts.Fred

[slow car]

The rear defuser is fed by a flat sculptured floor the front splitter has 2 defuesers built into it.Great lap time improvements.
Webby

[Jeff Alton]

And the latest 3.2SS that just got tuned. Ambient temps were a wee it lower for this one, hovering around 10C.

[lvporschepilot]

That's fabulous! Wow. what cam is that with?

[Gabe.]

Wow, that's awesome! Also curious on Cam. That DC44 seems like a great fit.

[Jeff Alton]

Originally Posted by gabe.

wow, that's awesome! Also curious on cam. That dc44 seems like a great fit.

dc44-110

[sp_cs]

Does that debunk the theory of SSIs being restrictive?

Also, how does a 3.2 out-torque a 3.4 - my simple brain does not compute?

[Gabe.]

What factors helped you decide to do a Lobe Separation Angle of 110 on the 3.2 and 108 on the 3.4? Thanks for educating us!

[Jeff Alton]

Originally Posted by Gabe.

What factors helped you decide to do a Lobe Separation Angle of 110 on the 3.2 and 108 on the 3.4? Thanks for educating us!

Discussions with the cam grinder about the client's needs. John has far more experience in the details of what each of his cams can provide. Mining knowledge and experience from others is part of what helps us learn. I wish I could say I had a secret formula...

Cheers

[Jeff Alton]

Originally Posted by sp_cs

Does that debunk the theory of SSIs being restrictive?

Also, how does a 3.2 out-torque a 3.4 - my simple brain does not compute?

Every engine is a sum of its parts and they all need to work well together. I believe there is more power and torque in the 3.4 (remember we ran out of injector). We also did not have control over the exhaust, it was already on the car, and although a good sizing for the displacement, the tube length and muffler design likely are not optimal.

Trumpet length, butterfly placement and injector placement are all factors as well. I would love the budget to fully optimize and test various configurations.

Have done limited back to back dyno testing with open velocity stacks vs tea strainers vs typical K+N Watersheild style filter, but would love the time and budget to do more. I love finding what works, and debunking myths like we did with the filter tests on 2 different motors.

Cheers

[sp_cs]

Thanks Jeff - you may have seen my dyno graph floating around on a few threads.

This is a 3.4 with GT3 crank, 45mm ATPower, twin plug, 11.5:1, motec, William Knight (Elgin) cams, Eisenmann 42mm OD SSIs. Thin lines with stacks, thick lines are 993 plenum. The map for the stacks was tidied up after the graph was plotted so some of the ‘waves’ will have been reduced.

[KTL]

This thread is useless, absent of engine pictures.

[Jeff Alton]

The 3.4....



The 3.2SS...








Cheers

[Travis Neff]

That torque curve on the 3.2ss is impressive, especially down low. Can i ask which port sizes you went for? I hear that big ports kill low end torque

[Jeff Alton]

Travis, we used the stock small port sizes, just had them cleaned up in the guide area and then the manifolds for the itbs were matched to the ports.

Cheers

[Jeff Alton]

Our Dyno Tuning shop, Statified Automotive Controls, asked if they could get their hands back on the 3.4. We obliged. This was the first AEM Infinity they had tuned. Once they tuned the 3.2SS they thought they could coax a bit more power out of the 3.4. And they did....

An additional 16 WHP and 9 lb/ft. Very pleased.

Can't wait to see what they do with the 3.8 next week!!



Cheers

[icarp]

Originally Posted by Jeff Alton

Travis, we used the stock small port sizes, just had them cleaned up in the guide area and then the manifolds for the itbs were matched to the ports.

Cheers

Small port size meaning 34 mm from the stock 80-83 3.0 engine ?
Or 39.5 from 78-79/ or the 42.5 from the 3.2?
thanks Jeff , great job