No knock in third but knock in 4th?

[re-rx7]

Ive been struggling lately with knock. If i wot 1-3 is fine 4th is giving me knock at around 5400. If at Hwy speeds downshift from 5th to 3rd no knock till i hit around 5300 in 4th. I dont understand why it knocks in 4th. Is it because its a long gear pull? I dont have a log and im on a hahn big smic with evo
Injectors. Tuning with ecu flash.

 

[MY1GDSM]

What kind of timing are you seeing right before your start seeing knock? Any Idea what your AIT's are after a pull in 4th vs 3rd? That's right around Peak Tq. what are your AFR's then as well? your also more then likely going to be seeing higher load in 4th what kind of boost are you running? what are your IDC's?

There are a lot of things to factor in in and not a lot of info to go off of aside from the fact you don't have a FMIC and probably seeing so fairly high AIT's... .

 

[re-rx7]

Info i do know. I have a tuner that tunes the car. Afr is around 11.0 flat and i know my max timing is 11-12 degrees. Running 18-19 psi on a t28. Would i still see high iat's even with the hahn big smic? Arrgghh so confusing.

 

[Pipnorcali]

My old Hahn fmic flows very poorly and Lucas thought I should swap it for a better one ( ets) so I would think your SMIC would be even worse

I was getting pretty high ait's at the track till I made a home made air box

 

[re-rx7]

I may buy a Trust/Greddy FMIC froom my friend this week. I was trying to stay away from buying a FMIC because of the lack of airflow. I guess you gotta pay to play. On another note, I did a quick run on the way to work this morning (mid 50's) and noticed the knock came on about 500-700 rpm later than usual so it very well could be the IC. Im going to try and trim the duct for it a little today and see what happens.

 

[MY1GDSM]

I may buy a Trust/Greddy FMIC froom my friend this week. I was trying to stay away from buying a FMIC because of the lack of airflow. I guess you gotta pay to play.

I wouldn't bother with many FMIC's aside from a ETS... Just do as the Last poster was advised and you won't regret it as you said you gotta pay to play... .

Lack of airflow

 

[Pipnorcali]

I think he means airflow to his rad, but yea at least try to get some more air over your smic

 

[2deep]

Sounds like heat-soak to me. How much boost are you running? Your low timing could be causing high EGTs too. I run more timing on pump gas at 24psi with a 10:1cr motor.

 

[MY1GDSM]

The HTA86 in your profile probably has a LOT cooler air charge coming out of it at 24 psi then the OP's T-2 small @ 18-19 psi... . Not to mention you run meth injection?

Info i do know. I have a tuner that tunes the car. Afr is around 11.0 flat and i know my max timing is 11-12 degrees. Running 18-19 psi on a t28. Would i still see high iat's even with the hahn big smic? Arrgghh so confusing.

Yes if you want pick up a semi cheap laser heat gun and pull over after and shot it at the IC I think you might be surprised just how high you AIT's probably are.

This would help matters out or if that's to much $$$ then look for one used. Can't go wrong with ETS

 

[2deep]

The HTA86 in your profile probably has a LOT cooler air charge coming out of it at 24 psi then the OP's T-2 small @ 18-19 psi... . Not to mention you run meth injection?

Different set-up. The HTA86 was ran at 36psi and 13* timing with meth.

The 24psi pump gas tune was with an HTA68. I'm running 12* uptop with sunoco 94, no meth. I havent tried to get any more timing, just trying to get more boost out of the lil guy. The HTA68 has been on the car for 2 days.

If the OP is really running a T-25, then he is most likely knocking knocking due to heat-soak.

 

[MY1GDSM]

Either way it's not a good comparison IMO as anything that is more efficient is going to have cooler Ait's and regardless comparing even Identical cars isn't going to get anyone every far Way to many factors to take into consideration... .

 

[2deep]

You would figure a car with 8.5:1CR running 18psi, would be able to get away with more timing than a 10:1cr motor running 24psi. I realize I have a much more effiecient set-up, but I still believe he should be able to get away with more timing with a much lower compression motor AND lower boost, which in turn will lower EGTs.

Again, I believe the root to his problem is he's simply heat-soaking his sidemount, his T-25 is ineffecient at those boost levels. He definitely needs a better cooler.

 

[daren_p]

I ran the HRC SMIC years back, I will say a good FMIC is defently a much better choice. Your probably right at the limits of that core. With 4th being abit more load, & if your running a typical MBC this will typically make your boost slightly higher in 4th as well. Your probably right on the edge of knocking in 3rd, so this extra load &/or boost in 4th is enough for slight knock.

Either fatten up the tune abit so it doesn't knock in 4th or switch to a FMIC & go form there.

 

[re-rx7]

Jesus. Its not a t25. Its fp28! At 18-19 psi right in its sweet spot. Im gna try and bunp up the fuel a few points if it doesnt work i will drop timing again. . I know the high egt's arent helping either.

 

[MY1GDSM]

Jesus. Its not a t25. Its fp28!

Sorry misread that, either way I was just saying that in comparison the Air charge is going to be higher... .

Either way the Best solution I see is a better intercooler who runs a Sidemount these days any way

 

[re-rx7]

Lol aint that the truth. The greddy fmic is probally better than what im running now anyway. I rigged a intercooler sprayer up today and that didnt help either. Im just worried about texas and the summer. It will be 100+ degrees. I may save up for rad first then get the fmic. I honestly thought the smic would the job. Wasted 200$.
S/n im not running a bc. The turbo creeps to 19 psi and stays put there. So basically just running wg

 

[1996dsm]

^ hey whats up man, Im sure my co-worker josh might take your smic off your hands if you want to sell it.

 

[re-rx7]

Get on Dallasdsm. I may post it up for sale. Its pretty much brand new.

I ran the HRC SMIC years back, I will say a good FMIC is defently a much better choice. Your probably right at the limits of that core. With 4th being abit more load, & if your running a typical MBC this will typically make your boost slightly higher in 4th as well. Your probably right on the edge of knocking in 3rd, so this extra load &/or boost in 4th is enough for slight knock.

Either fatten up the tune abit so it doesn't knock in 4th or switch to a FMIC & go form there.

Tried the richening it up and so far it hasnt worked. I firmly believe i can get it to work. Which would be great because i dont want any more power than what it is making. I want maximum airflow through that radiator. Interestingly enough today on the way to work it did the same thing as usual but after a few hundred rpm the knock went away and it went back to normal?

 

[MY1GDSM]

I don't think that your airflow to the radiator is going to be as bad as you think(at least with what I recommended)

I'm interested to see a log, what are your AIT's anyway never did say?

You should try to pull a degree or so timing just around peak Tq at your highest load cell your hitting just to see as long as long as it doesn't make the map have any drastic changes from the other cells an see what it does your more likely to be prone to knock there then are were else Imo... .

 

[re-rx7]

I don't think that your airflow to the radiator is going to be as bad as you think(at least with what I recommended)

I'm interested to see a log, what are your AIT's anyway never did say?

You should try to pull a degree or so timing just around peak Tq at your highest load cell your hitting just to see as long as long as it doesn't make the map have any drastic changes from the other cells an see what it does your more likely to be prone to knock there then are were else Imo... .

Im gna fix some of the gap in my stock duct to intercooler. You mean take out a degree or two of timing in the 500-6000 rpm range?>

 

[JaySyn77]

He means to take a degree or 2 of timing in the rpm range where you're seeing the knock. For example, you mention knocking around 5300 in 4th...go to 5000 rpm and 5500rpm and take away a degree. Go out for a drive and see if it takes away or reduces the knock.

 

[re-rx7]

I mis-typed. Thats what im gna do. I really need to invest in the tactrix cable. Im gna try and get down there today and get a log of my IAT's.

Going back to get him to look at it today.

 

[daren_p]

Get on Dallasdsm. I may post it up for sale. Its pretty much brand new.


Tried the richening it up and so far it hasnt worked. I firmly believe i can get it to work. Which would be great because i dont want any more power than what it is making. I want maximum airflow through that radiator. Interestingly enough today on the way to work it did the same thing as usual but after a few hundred rpm the knock went away and it went back to normal?

When I mentioned "fatten" up your tune, I just ment to make it less aggressive in the typical problem area in general (not just add more fuel). As mentioned elsewhere, pulling a deg or two in the problem (&/or the rpms just before the knock) area should help the issue.